Acoustic resonator structure with inclined c-axis piezoelectric bulk and crystalline seed layers

ABSTRACT

Systems and methods for growing hexagonal crystal structure piezoelectric material with a c-axis that is tilted (e.g., 25 to 50 degrees) relative to normal of a face of a substrate are provided. A deposition system includes a linear sputtering apparatus, a translatable multi-aperture collimator, and a translatable substrate table arranged to hold multiple substrates, with the substrate table and/or the collimator being electrically biased to a nonzero potential. An enclosure includes first and second deposition stations each including a linear sputtering apparatus, a collimator, and a deposition aperture.

STATEMENT OF RELATED APPLICATIONS

This application is a non-provisional of U.S. Provisional PatentApplication No. 62/241,264 filed on Oct. 14, 2015, wherein the entirecontents of the foregoing application is hereby incorporated byreference as if set forth fully herein. Subject matter disclosed hereinalso relates to the following four U.S. patent applications each filedor to be filed on Oct. 14, 2016, and each claiming priority to U.S.Provisional Patent Application No. 62/241,264: (1) U.S. patentapplication Ser. No. ______ entitled “Deposition System for Growth ofInclined C-Axis Piezoelectric Material Structures;” (2) U.S. patentapplication Ser. No. ______ entitled “Methods for Fabricating AcousticStructure with Inclined C-Axis Piezoelectric Bulk and Crystalline SeedLayers;” (3) U.S. patent application Ser. No. ______ entitled“Multi-Stage Deposition System for Growth of Inclined C-AxisPiezoelectric Material Structures;” and (4) U.S. patent application Ser.No. ______ entitled “Methods for Producing Piezoelectric Bulk andCrystalline Seed Layers of Different C-Axis Orientation Distributions,”wherein the contents of the foregoing four U.S. patent applications arehereby incorporated by reference as if set forth fully herein.

TECHNICAL FIELD

The present disclosure relates to structures including inclined c-axishexagonal crystal structure piezoelectric materials such as aluminumnitride (AlN) and zinc oxide (ZnO), as well as systems and methods forproducing inclined c-axis hexagonal crystal structure piezoelectricmaterial. Inclined c-axis hexagonal crystal structure piezoelectricmaterials may be used, for example, in various resonators as well as inthin film electroacoustic and/or sensor devices, particularly forsensors operating in liquid/viscous media (e.g., chemical andbiochemical sensors), and the like.

BACKGROUND

Hexagonal crystal structure piezoelectric materials such as AlN and ZnOare of commercial interest due to their piezoelectric andelectroacoustic properties. Beneficial properties in this regard includea high quality factor, moderate coupling coefficient, moderatepiezoelectric constant, high acoustic velocity, and low propagationlosses. In addition to these characteristics, AlN thin films arechemically stable and compatible with various integrated circuitfabrication technologies, thereby making AlN an attractive material forfabrication of electroacoustic devices, including bulk acoustic wave(BAW) devices such as bandpass filters and the like.

A primary use of electroacoustic technology has been in thetelecommunication field (e.g., for oscillators, filters, delay lines,etc.). More recently, there has been a growing interest in usingelectroacoustic devices in high frequency sensing applications due tothe potential for high sensitivity, resolution, and reliability.However, it is not trivial to apply electroacoustic technology incertain sensor applications—particularly sensors operating inliquid/viscous media (e.g., chemical and biochemical sensors)—sincelongitudinal and surface waves exhibit considerable acoustic leakageinto such media, thereby resulting in reduced resolution.

In the case of a piezoelectric crystal resonator, an acoustic wave mayembody either a bulk acoustic wave (BAW) propagating through theinterior (or ‘bulk’) of a piezoelectric material, or a surface acousticwave (SAW) propagating on the surface of the piezoelectric material. SAWdevices involve transduction of acoustic waves (commonly includingtwo-dimensional Rayleigh waves) utilizing interdigital transducers alongthe surface of a piezoelectric material, with the waves being confinedto a penetration depth of about one wavelength. BAW devices typicallyinvolve transduction of an acoustic wave using electrodes arranged onopposing top and bottom surfaces of a piezoelectric material. In a BAWdevice, different vibration modes can propagate in the bulk material,including a longitudinal mode and two differently polarized shear modes,wherein the longitudinal and shear bulk modes propagate at differentvelocities. The longitudinal mode is characterized by compression andelongation in the direction of the propagation, whereas the shear modesconsist of motion perpendicular to the direction of propagation with nolocal change of volume. The propagation characteristics of these bulkmodes depend on the material properties and propagation directionrespective to the crystal axis orientations. Since shear waves exhibit avery low penetration depth into a liquid, a device with pure orpredominant shear modes can operate in liquids without significantradiation losses (in contrast with longitudinal waves, which can beradiated in liquid and exhibit significant propagation losses).Restated, shear mode vibrations are beneficial for operation of acousticwave devices with fluids because shear waves do not impart significantenergy into fluids.

Certain piezoelectric thin films are capable of exciting bothlongitudinal and shear mode resonance. To excite a wave including ashear mode using a standard sandwiched electrode configuration device, apolarization axis in a piezoelectric thin film must generally benon-perpendicular to (e.g., tilted relative to) the film plane.Hexagonal crystal structure piezoelectric materials such as (but notlimited to) aluminum nitride (AlN) and zinc oxide (ZnO) tend to developtheir polarization axis (i.e., c-axis) perpendicular to the film plane,since the (0001) plane typically has the lowest surface density and isthermodynamically preferred. Certain high temperature (e.g., vapor phaseepitaxy) processes may be used to grow tilted c-axis films, butproviding full compatibility with microelectronic structures such asmetal electrodes or traces requires a low temperature deposition process(e.g., typically below about 300° C.).

Low temperature deposition methods such as reactive radio frequencymagnetron sputtering have been used for preparing tilted AlN filmshaving angles that vary significantly with position over the area of asubstrate. FIG. 1 is a simplified schematic of an axial sputteringdeposition apparatus arranged to eject metal atoms from a target 2(adjacent to a cathode (not shown)) toward a substrate 4 supported by asubstrate holder 6 that is substantially parallel to the target 2 in areactive gas-containing environment. The target 2 and the substrate 4are aligned with one another and share a single central axis 8; however,a typical geometry of sputtering deposition results in a cosinedistribution 10 of piezoelectric material molecules (e.g., AlN moleculescreated by metal atoms reacting with nitrogen in the sputtering gas)being received by the substrate 4. This phenomenon leads to a c-axisdirection of the deposited piezoelectric material that varies withradial position, from an angle of zero (corresponding to a verticalc-axis) at the center of the substrate 4, to a c-axis direction with atilt angle that increases with distance from the center.

The above-described variation with radial position of c-axis directionof a deposited piezoelectric material is disclosed by Stan, G. E., etal., “Tilt c Axis Crystallite Growth of Aluminium Nitride Films byReactive RF-Magnetron Sputtering,” Digest Journal of Nanomaterials andBiostructures, vol. 7, no. 1, pp. 41-50 (2012) (hereinafter, “Stan”).FIG. 2A is a schematic representation (reproduced from Stan) of arocking curve measurement geometry of an AlN film structure obtained byradio frequency magnetron sputtering in a reactive gas environment in anaxially aligned planar sputtering system without tilting a 50 mm Sisubstrate. FIG. 2A shows that the AlN film structure according to Stanexhibits zero c-axis tilt angle at the center, and a radiallysymmetrical variation of tilt angle of crystallites in the AlN filmstructure, analogous to a circular “race track” with banked walls. FIG.2B is a plot of tilt angle versus distance from center (also derivedfrom Stan) for the AlN film structure described in connection with FIG.2A, showing a nearly linear variation of tilt angle with increasingdistance away from a center of the AlN film structure, to a maximum tiltangle of about 6.5 degrees near the margins of the 50 mm wafer. Oneeffect of the lack of uniformity of c-axis tilt angle of the AlN filmstructure over the substrate is that if the AlN film-covered substratewere to be diced into individual chips, the individual chips wouldexhibit significant variation in c-axis tilt angle and concomitantvariation in acoustic wave propagation characteristics. Such variationin c-axis tilt angle would render it difficult to efficiently producelarge numbers of resonator chips with consistent and repeatableperformance. Moreover, use of a target surface axially aligned with asubstrate holder that is parallel to the target surface enablesattainment of only a limited range of c-axis tilt angles, as evidencedby the 0-6.5 degree tilt angle range shown in FIG. 2A.

Before describing other techniques for preparing tilted AlN films,desirable regimes for c-axis tilt angle (or angle of inclination) willbe discussed. An electromechanical coupling coefficient is a numericalvalue that represents the efficiency of piezoelectric materials inconverting electrical energy into acoustic energy for a given acousticmode. Changing the c-axis angle of inclination for hexagonal crystalstructure piezoelectric materials causes variation in shear andlongitudinal coupling coefficients, as shown in FIG. 3. FIG. 3 embodiesplots of shear coupling coefficient (K_(s)) and longitudinal couplingcoefficient (K_(l)) each as a function of c-axis angle of inclinationfor AlN. It can be seen that a maximum electromechanical couplingcoefficient of shear mode resonance in AlN is obtained at a c-axis angleof inclination of about 35 degrees, that a pure shear response (withzero longitudinal coupling) is obtained at a c-axis angle of inclinationof about 46 degrees, and that the shear coupling coefficient exceeds thelongitudinal coupling coefficient for c-axis angle of inclination valuesin a range of from about 19 degrees to about 63 degrees. Thelongitudinal coupling coefficient is also zero at a c-axis angle ofinclination of 90 degrees, but it is impractical to grow AlN at verysteep c-axis inclination angles. For electroacoustic resonators intendedto operate in liquids or other viscous media, it would be desirable toprovide piezoelectric films with a c-axis tilt angle sufficient toprovide a shear coupling coefficient that exceeds a longitudinalcoupling coefficient—in certain embodiments, at a c-axis tilt angle inwhich the longitudinal coupling coefficient approaches zero, or at ac-axis-tilt angle at or near a value where shear coupling is maximized.Thus, for an electroacoustic resonator including an AlN piezoelectriclayer, it would be desirable to provide a c-axis tilt angle in a rangeof from about 19 degrees to about 63 degrees, and particularly desirableto provide a c-axis tilt angle of 35 or 46 degrees.

Various low temperature deposition methods that have been devised forgrowing AlN films at c-axis tilt angles greater than those attainablewith the axial sputtering apparatus of FIG. 1 are described inconnection with FIGS. 4A-4C. FIG. 4A (which is adapted from Moreira,Milena De Albuquerque, “Synthesis of Thin Piezoelectric AlN Films inView of Sensors and Telecom Applications,” 2014, Digital ComprehensiveSummaries of Uppsala Dissertations from the Faculty of Science andTechnology, 1651-6214; 1160) (hereinafter, “Moreira”) is a simplifiedschematic of an off-axis sputtering deposition apparatus arranged toeject metal atoms from a target surface 12 toward a substrate 14supported by a substrate holder 16 that is substantially parallel to thetarget surface 12, with central axes of the substrate 14 and the targetsurface 12 being parallel but offset relative to one another, with anangle θ representing an angle between a central axis 18 of the targetsurface 12 and a center of the substrate 14. A distribution 20 ofpiezoelectric material molecules created by reaction of metal atoms andgas is received by the substrate 14, resulting in a tilted c-axisdirection of deposited piezoelectric material (including tilted‘columns’ of piezoelectric material with a preferential growth directiondue to alignment with the tilted flux), with the c-axis tilt angle ofthe piezoelectric material varying with respect to position along thesubstrate 14. In particular, a portion of the deposited piezoelectricmaterial that is closer to the central axis 18 of the target surface 12will exhibit a c-axis tilt angle that is shallower than a portion of thepiezoelectric material that is farther from the central axis 18 of thetarget surface 12. Due to the lateral offset of the substrate 14relative to the central axis 18 of the target surface 12, the off-axissputtering deposition apparatus of FIG. 4A is capable of attainingpiezoelectric films with c-axis tilt angles that are larger than thoseattainable with the apparatus of FIG. 1.

Additional low temperature deposition sputtering apparatuses capable ofgrowing piezoelectric films with even larger c-axis tilt angles aredescribed in connection with FIGS. 4B and 4C (which are also adaptedfrom Moreira). FIG. 4B is a simplified schematic of a sputteringdeposition apparatus arranged to eject metal atoms from a target surface22 toward a substrate 24 supported by a substrate holder 26 that isnon-parallel to the target surface 22 (i.e., wherein the substrateholder 26 is tilted by an angle θ relative to a plane parallel with thetarget surface 22), wherein a central axis 28 of the target surface 22extends through a center point of the substrate 24. A distribution 30 ofpiezoelectric material molecules created by reaction of metal atoms andgas is received by the substrate 24, resulting in a tilted c-axisdirection of deposited piezoelectric material (including tilted‘columns’ of piezoelectric material with a preferential growth directiondue to alignment with the tilted flux), with the c-axis tilt angle ofthe piezoelectric material varying with respect to position along thesubstrate 24. FIG. 4C is a simplified schematic of a sputteringdeposition apparatus arranged to eject metal atoms from a target surface32 toward a substrate 34 supported by a substrate holder 36 that isnon-parallel to the target surface 32. A central axis 38B of thesubstrate 34 extends through a center point of the target surface 32,with a central axis 38A of the target surface 32 being separated fromthe central axis 38B of the substrate 34 by a first angle θ₁, and withsubstrate holder 36 being tilted by a second angle θ₂ relative to aplane parallel with the target surface 32. A distribution 40 ofpiezoelectric material molecules created by reaction of metal atoms andgas is received by the substrate 34, resulting in a tilted c-axisdirection of deposited piezoelectric material (including tilted‘columns’ of piezoelectric material with a preferential growth directiondue to alignment with the tilted flux), with the c-axis tilt angle ofthe piezoelectric material varying with respect to position along thesubstrate 34.

Yet another method for growing a tilted c-axis AlN film involvestwo-step sputtering deposition as described by Moreira, including firststep growth of an initial, non-textured seed layer at a relatively highprocess pressure while keeping the substrate at room temperature,followed by second step growth of a film at a lower process pressure andan elevated substrate temperature. FIG. 5A is a cross-sectionalschematic view of a seed layer 44 exhibiting multiple textures depositedvia the first sputtering step over a substrate 42, and FIG. 5B is asimilar view of the seed layer 44 and substrate 42 of FIG. 5A followingdeposition via a second sputtering step of a tilted axis AlN film 46over the seed layer 44. As described by Moreira, the seed layer exhibitsdifferent textures, most notably (103) and (002). Additionally, the filmgrowth tends to follow the crystallographic texture of the seed layer,and the low pressure deposition in combination with a small distancebetween the target and substrate yields a directional deposition fluxthat results in competitive column growth in which cones having a c-axisalong the direction of the deposition flux grow fastest. This results ina film with a c-axis lying in the plane of the deposition flux at anygiven point along the substrate. As noted by Moreira, even though thereis no intentional tilt of the flux, the magnetron disposition at thetarget surface generates a “race track”, which in turn provides thetilted flux direction towards the substrate. Such a “race track”described by Moreira is understood to correspond to a radially symmetricvariation of tilt angle of crystallites in the film structure, similarto that described hereinabove in connection with FIGS. 2A and 2B.

Each of the foregoing apparatuses and tilted piezoelectric materialgrowth methods are understood to produce film-covered substratesexhibiting significant variation in c-axis tilt angle with respect toposition on the substrate. As noted previously, one effect of a lack ofuniformity of c-axis tilt angle of a piezoelectric film arranged on thesubstrate is that if the film-covered substrate were to be diced intoindividual chips, then the individual chips would exhibit significantvariation in c-axis tilt angle and concomitant variation in acousticwave propagation characteristics. Such variation in c-axis tilt anglewould render it difficult to efficiently produce large numbers ofresonator chips with consistent and repeatable performance.

Accordingly, there is a need for systems and methods for producinginclined c-axis hexagonal crystalline material films over large areasubstrates without significant variation in c-axis tilt angle, such asto enable economical production of bulk acoustic wave resonatorstructures with repeatable performance characteristics. It would furtherbe desirable for such systems and methods to be compatible withintegrated circuit fabrication technologies and enable fabrication ofpiezoelectric films with c-axis tilt angles sufficient to provide highshear coupling coefficients, so as to enable production of resonatordevices suitable for use in liquids and other viscous media.

SUMMARY

The present disclosure provides bulk acoustic wave resonator structures,methods for fabricating such resonator structures, and depositionsystems suitable for producing inclined c-axis hexagonal crystalstructure piezoelectric material that may be incorporated in suchresonator structures. A bulk acoustic wave resonator structure includesa hexagonal crystal structure piezoelectric material bulk layer arrangedover a crystalline seed layer and supported by a substrate, wherein atleast 50% (or at least 75%, or at least 90%, or at least 95%) of thebulk layer includes a c-axis with an orientation distributionpredominantly in a range of from 25 degrees to 50 degrees (or in asubrange of from 30 degrees to 40 degrees) relative to normal of a faceof the substrate. Such c-axis orientation distribution is preferablysubstantially uniform over the area of a large area substrate (e.g.,having a diameter in a range of at least about 50 mm, about 100 mm, orabout 150 mm), thereby enabling multiple chips having the same orsimilar acoustic wave propagation characteristics to be derived from asingle substrate. A deposition system suitable for growing tilted c-axishexagonal crystal structure piezoelectric material includes a linearsputtering apparatus, a multi-aperture collimator, and a translatablesubstrate table having a support surface arranged non-parallel to atarget surface of the linear sputtering apparatus, with the substratetable and/or the collimator being electrically biased to a potentialother than ground. In certain embodiments, the collimator is groundedwhile the substrate table is electrically biased, or vice-versa. Anotherdeposition system includes multiple linear sputtering apparatuses, asubstrate table that is translatable between different positionsproximate to different linear sputtering apparatuses, and multiplecollimators arranged between the substrate table and the respectivelinear sputtering apparatuses, with a support surface of the substratetable being non-parallel to at least one target surface of the differentlinear sputtering apparatuses. A method for fabricating at least onebulk acoustic wave resonator structure includes growth of a crystallineseed layer over at least one resonator device complex during a firststep, followed by growth of a hexagonal crystal structure piezoelectricmaterial bulk layer of a defined c-axis distribution range (e.g., fromabout 25 degrees to 50 degrees, or 30 to 40 degrees, relative to normalof a face of a substrate), with at least one of the growth stepsincluding transit of metal atoms from a target surface of a linearsputtering apparatus through a collimator and a deposition aperture toreact with a gas species and be received by the at least one resonatordevice complex, and with the target surface being arranged non-parallelto a substrate. Another method for fabricating at least one bulkacoustic wave resonator structure utilizes a substrate table that ismovable between first and second stations including first and secondlinear sputtering apparatuses and a first collimator (optionally,further including a second collimator), wherein a crystalline seed layeris grown by reactive sputtering in the first station, and a hexagonalcrystal structure piezoelectric material bulk layer comprising adifferent c-axis orientation distribution than the crystalline seedlayer is grown by reactive sputtering in the second station.

In one aspect, a deposition system includes a linear sputteringapparatus including a target surface configured to eject metal atoms; asubstrate table including a support surface that is configured toreceive at least one wafer and is coupled to a translation element,wherein the translation element is configured to translate the substratetable and the at least one wafer during operation of the linearsputtering apparatus; and a collimator including a plurality of guidemembers defining a plurality of collimator apertures arranged betweenthe linear sputtering apparatus and the substrate table; wherein thetarget surface is arranged non-parallel to the support surface; andwherein at least one of the substrate table or the collimator iselectrically biased to a potential other than ground.

In certain embodiments, the plurality of guide members of a collimatoris arranged non-perpendicular to the support surface. The guide memberspreferably serve to redirect metal atoms ejected by the target surfacetoward the support surface to reduce variability in atom trajectory andthereby promote uniformity (e.g., in c-axis tilt angle) of materialdeposition. In certain embodiments, only the substrate table or only thecollimator is electrically biased to a potential other than ground; inother embodiments, each of the substrate table and the collimator iselectrically biased to a potential other than ground. Electrical biasingof the substrate table and/or the collimator desirably enhances controlof material deposition, while movement (e.g., translation) of the atleast one wafer during sputtering may desirably promote uniform materialdeposition.

In certain embodiments, the linear sputtering apparatus comprises alinear magnetron that includes a sputtering cathode operatively coupledto the target surface to promote ejection of metal atoms from the targetsurface. In other embodiments, the linear sputtering apparatus comprisesa linear ion beam sputtering apparatus. In certain embodiments, thecollimator is configured to move (e.g., translate) during operation ofthe linear sputtering apparatus. Movement of the collimator duringsputtering desirably prevents formation of “shadow” pattern(corresponding to the shape and position of guide members of thecollimator) that would otherwise be formed on a surface receivingpiezoelectric material following transit of metal atoms through thecollimator. In alternative embodiments, a rotating magnetron may be usedin lieu of a linear magnetron.

In certain embodiments, the plurality of guide members includes aplurality of longitudinal members and a plurality of transverse membersthat form a grid. In certain embodiments, the plurality of guide membersincludes a plurality of longitudinal members biased to a firstelectrical potential other than ground and includes a plurality oftransverse members biased to a second electrical potential other thanground, and wherein the second electrical potential differs from thefirst electrical potential. Electrically biasing different groups ofguide members may desirably enhance control of material deposition.

In certain embodiments, the deposition system further includes adeposition aperture arranged between the collimator and the substratetable. In certain embodiments, the deposition system further includes auniformity shield configured to adjust dimensions (e.g., size and shape)of the deposition aperture. Utilization of a uniformity shield maydesirably prevent localized accumulation of deposited material on asubstrate or resonator device complex that could otherwise result inundesirable thickness variation of a deposited film.

In certain embodiments, the support surface is configured to receivemultiple (e.g., at least two, at least three, at least four, or five ormore) wafers. In certain embodiments, the target surface includesaluminum or zinc and is configured to eject aluminum atoms or zincatoms, such as may be useful for deposition of aluminum nitride or zincoxide films. Other metals may be used for formation of hexagonal crystalstructure piezoelectric materials other than aluminum nitride and zincoxide. In certain embodiments, the target surface is oriented 15 to 55degrees apart from the substrate table.

In certain embodiments, the deposition system is configured to receive asupply of sputtering gas, wherein the sputtering gas includes a gasspecies adapted to react with the metal atoms. In certain embodiments,the deposition system is operatively coupled to a source of sputteringgas including nitrogen (such as may be useful to react with aluminumions to form aluminum nitride). In certain embodiments, the depositionsystem is operatively coupled to a source of sputtering gas includingoxygen (such as may be useful to react with zinc ions to form zincoxide). Other gas constituents may be present, such as (but not limitedto) argon or other noble gases.

In certain embodiments, the deposition system includes at least onewafer received by the support surface, wherein the at least one waferincludes a substrate, an acoustic reflector structure arranged over thesubstrate, and an electrode structure arranged over at least a portionof the acoustic reflector structure. In certain embodiments, followingdeposition of a hexagonal crystal structure piezoelectric material bulklayer over the acoustic reflector structure and the electrode structure,a second electrode structure may be formed over the hexagonal crystalstructure piezoelectric material to form a bulk acoustic wave resonatorstructure. In certain embodiments, the deposition system includes atleast one wafer received by the support surface, wherein the at leastone wafer includes a substrate defining a recess, a support layer isarranged over the recess, and an electrode structure is arranged overthe support layer.

In certain embodiments, the deposition system is configured for growthof a hexagonal crystal structure piezoelectric material bulk layer overa seed layer that overlies a wafer received by the support surface,wherein at least 50% (or at least 75%, or at least 90%, or at least 95%)of the hexagonal crystal structure piezoelectric material bulk layerincludes a c-axis having an orientation distribution predominantly in arange of from 25 degrees to 50 degrees (or in a subrange of from 30degrees to 40 degrees) relative to normal of a face of the wafer.

In another aspect, a method for fabricating at least one bulk acousticwave resonator structure includes a first growth step includingdeposition of a crystalline seed layer over at least one resonatordevice complex, wherein each resonator device complex of the at leastone resonator device complex includes a substrate and at least one firstelectrode structure arranged over at least a portion of the substrate;and a second growth step including deposition of a hexagonal crystalstructure piezoelectric material bulk layer over the crystalline seedlayer that is arranged over the at least one resonator device complex,and being configured to yield at least 50% (or at least 75%, or at least90%, or at least 95%) of the hexagonal crystal structure piezoelectricmaterial bulk layer including a c-axis having an orientationdistribution predominantly in a range of from 25 degrees to 50 degrees(or in a subrange of from 30 degrees to 40 degrees) relative to normalof a face of the substrate; wherein at least one of the first growthstep or the second growth step includes ejection of metal atoms from atarget surface of a linear sputtering apparatus to (i) transit through acollimator including multiple collimator apertures and through adeposition aperture, and (ii) react with a gas species and be receivedby the at least one resonator device complex, wherein the target surfaceis arranged non-parallel to a face of the substrate. In certainembodiments, the crystalline seed layer is compositionally matched tothe hexagonal crystal structure piezoelectric material bulk layer.

In certain embodiments, the method further includes forming at least onesecond electrode structure over at least one portion of the hexagonalcrystal structure piezoelectric material bulk layer, such as may beuseful to form at least one bulk acoustic wave resonator device. Incertain embodiments, the method further includes roughening a backsideof the substrate after said forming of the at least one second electrodestructure. Such roughening may desirably reduce or eliminate acousticreflections from the backside surface of the substrate.

In certain embodiments, the first growth step is configured to yield atleast 50% (or at least 75%, or at least 90%, or at least 95%) of thecrystalline seed layer including a c-axis having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the substrate. In certain embodiments,the second growth step is configured to yield at least 90% (or at least75%, or at least 95%) of the hexagonal crystal structure piezoelectricmaterial bulk layer including a c-axis having an orientationdistribution predominantly in a range of from 25 degrees to 50 degreesrelative to normal of a face of the substrate.

In certain embodiments, the first growth step is performed at adeposition pressure in a range of from about 5 mT to about 50 mT, or ina range of from 5 mT to about 25 mT, or in a range of from about 10 mTto about 15 mT. In certain embodiments, the first growth step isperformed at a first deposition pressure, the second growth step isperformed at a second deposition pressure, and the first depositionpressure is greater than the second deposition pressure. In certainembodiments, the second deposition pressure is less than about 5 mT,less than about 3 mT, less than about 2 mT, or less than about 1 mT. Incertain embodiments, at least one of the first growth step or the secondgrowth step further includes moving (e.g., translating) the collimatorduring sputtering.

In certain embodiments, each resonator device complex of the at leastone resonator device complex comprises an acoustic reflector structurearranged between the substrate and the at least one first electrodestructure. In other embodiments, each resonator device complex of the atleast one resonator device complex includes a substrate defining arecess, with a support layer arranged over the recess, wherein the atleast one first electrode structure is arranged over the support layer.

In certain embodiments, the target surface is oriented 15 to 55 degreesapart from a face of the substrate and/or the substrate table supportingthe substrate. In certain embodiments, the target surface includesaluminum or zinc and is configured to eject aluminum atoms or zincatoms.

In certain embodiments, for each resonator device complex of the atleast one resonator device complex, the substrate includes a diameter ofat least about 50 mm (or at least 100 mm, or at least 150 mm). Incertain embodiments, the at least one resonator device complex includesa plurality of resonator device complexes. In certain embodiments, theat least one resonator device complex is supported by a substrate table,and the method further includes translating the substrate table duringthe first growth step and during the second growth step.

In certain embodiments, the first growth step includes ejection of metalatoms from a first target surface of a first linear sputtering apparatuslocated at a first station to (i) transit through a first depositionaperture (optionally preceded by transit through a first collimatorincluding a first group of collimator apertures), and (ii) react with atleast one gas species and be received by the at least one resonatordevice complex to deposit the crystalline seed layer over the at leastone resonator device complex; the method further includes moving thesubstrate table to move the at least one resonator device complexsupported by the substrate table to a second station containing a secondlinear sputtering apparatus; and the second growth step includesejection of metal atoms from a second target surface of the secondlinear sputtering apparatus to (i) transit through a second collimatorincluding a second group of collimator apertures and through a seconddeposition aperture, and (ii) react with at least one gas species and bereceived by the at least one resonator device complex to deposit thehexagonal crystal structure piezoelectric material bulk layer over thecrystalline seed layer of the at least one resonator device complex. Incertain embodiments, the first station and the second station arearranged in a single enclosure with at least one vacuum pumping elementconfigured to generate at least one subatmospheric pressure conditionwithin the enclosure, such that the second growth step may be performedin a sequential manner in a subatmospheric environment following thefirst growth step without any need for removing the at least oneresonator device complex into an atmospheric pressure environment beforethe second growth step (e.g., which would otherwise require significanttime and energy to establish subatmospheric conditions in a secondenclosure). In certain embodiments, the first station is located in afirst chamber having an associated first vacuum pumping element, and thesecond station is located in a second chamber having an associatedsecond vacuum pumping element.

In certain embodiments, the method further includes electrically biasingto a potential other than ground one or more of the following items: thesubstrate table, the first collimator, or the second collimator, duringat least one of the first growth step or the second growth step. Incertain embodiments, the method further includes translating the firstcollimator during operation of the first linear sputtering apparatus,and translating the second collimator during operation of the secondlinear sputtering apparatus. Movement of the first collimator and thesecond collimator during sputtering desirably prevents formation of“shadow” pattern (corresponding to the shape and position of guidemembers of the respective collimators) that would otherwise be formed ona surface receiving crystalline seed material during the first growthstep and a surface receiving piezoelectric material during the secondgrowth step. In certain embodiments, the substrate table and at leastone collimator are translated during operation of the linear sputteringapparatus during at least one of the first growth step or the secondgrowth step, wherein a direction of translation of the collimator issubstantially perpendicular to a direction of translation of thesubstrate table.

In certain embodiments, the method further includes dicing the at leastone resonator device complex, over which the hexagonal crystal structurepiezoelectric material bulk layer and the crystalline seed layer aredeposited, into a plurality of chips. In certain embodiments, each chipof the plurality of chips includes a solidly mounted bulk acoustic waveresonator chip or a film bulk acoustic wave resonator chip.

In another aspect, a bulk acoustic wave resonator device is produced bya method disclosed herein.

In another aspect, an acoustic resonator structure includes a substrate;at least one first electrode structure supported by the substrate; acrystalline seed layer arranged over the substrate and the at least onefirst electrode structure; a hexagonal crystal structure piezoelectricmaterial bulk layer arranged over the crystalline seed layer; and atleast one second electrode structure arranged over at least a portion ofthe hexagonal crystal structure piezoelectric material bulk layer;wherein at least 50% (or at least 75%, or at least 90%, or at least 95%)of the hexagonal crystal structure piezoelectric material bulk layerincludes a c-axis having an orientation distribution predominantly in arange of from 25 degrees to 50 degrees (or in a subrange of from 30degrees to 40 degrees) relative to normal of a face of the substrate.

In certain embodiments, the crystalline seed layer is compositionallymatched to the hexagonal crystal structure piezoelectric material bulklayer. In certain embodiments, a thickness of the crystalline seed layeris no greater than about 20%, no greater than about 15%, or no greaterthan about 10% of a combined thickness of the hexagonal crystalstructure piezoelectric material bulk layer and the crystalline seedlayer. In certain embodiments, the crystalline seed layer includes athickness in a range of from about 500 Angstroms to about 2,000Angstroms, and (for a hexagonal crystal structure seed material such asAlN) may include a dominant (103) texture. In certain embodiments, atleast 50% (or at least 75%, or at least 90%, or at least 95%) of thecrystalline seed layer includes a c-axis having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the substrate. In certain embodiments,the hexagonal crystal structure piezoelectric material bulk layerincludes a thickness in a range of from about 4,000 Angstroms to about26,000 Angstroms. Such bulk layer preferably includes substantiallyuniform thickness, nanostructure, and crystallinity properties. Suchbulk layer also preferably exhibits controlled stress and densely packedcolumnar grains or recrystallized grain structure.

In certain embodiments, the substrate includes a semiconductor material.In certain embodiments, an acoustic reflector structure is arrangedbetween the substrate and the at least one first electrode structure. Incertain embodiments, an acoustic reflector includes alternating layersof materials of different acoustic impedances (e.g., SiOC, Si₃N₄, SiO₂,AlN, and Mo), optionally embodied in a Bragg mirror. In certainembodiments, the substrate is arranged between a backside surface andthe acoustic reflector structure, and the backside surface comprises aroughened surface configured to reduce or eliminate backside acousticreflection.

In certain embodiments, the substrate defines a recess, a support layeris arranged over the recess, and the support layer is arranged betweenthe substrate and at least a portion of the at least one first electrodestructure.

In certain embodiments, at least 90% of the hexagonal crystal structurepiezoelectric material bulk layer includes a c-axis having anorientation distribution predominantly in a range of from 12 degrees to52 degrees, or from 25 degrees to 50 degrees, relative to normal of aface of the substrate. In certain embodiments, at least 50% (or at least75%, or at least 90%, or at least 95%) of the hexagonal crystalstructure piezoelectric material bulk layer includes a c-axis having anorientation distribution predominantly in a range of from 30 degrees to40 degrees relative to normal of a face of the substrate. In certainembodiments, less than about 3 percent of the c-axis orientationdistribution of the hexagonal crystal structure piezoelectric materialbulk layer is in a range of from 0 degrees to 15 degrees relative tonormal of a face of the substrate. In certain embodiments, a hexagonalcrystal structure piezoelectric material bulk layer includes a thicknessin a range of from 4,000 Angstroms to 26,000 Angstroms.

In certain embodiments, the substrate includes a diameter of at leastabout 50 mm (or at least 100 mm, or at least 150 mm), and the hexagonalcrystal structure piezoelectric material bulk layer covers at leastabout 50% (or at least about 75%, or at least about 90%) of a face ofthe substrate. In certain embodiments, the substrate includes a diameterof at least about 100 mm (or at least about 150 mm), and the hexagonalcrystal structure piezoelectric material bulk layer covers at leastabout 50% (or at least about 75%, or at least about 90%, or at leastabout 95%) of a face of the substrate.

In certain embodiments, the hexagonal crystal structure piezoelectricmaterial bulk layer includes aluminum nitride. In certain embodiments,the hexagonal crystal structure piezoelectric material bulk layerincludes zinc oxide. In certain embodiments, other hexagonal crystalstructure piezoelectric material may be used.

In certain embodiments, the at least one first electrode structureincludes a plurality of first electrode structures; the at least onesecond electrode structure includes a plurality of second electrodestructures; a first portion of the acoustic resonator structure includesa first bulk acoustic wave resonator device including a first activeregion arranged between one first electrode structure of the pluralityof first electrode structures and one second electrode structure of theplurality of second electrode structures; and a second portion of theacoustic resonator structure includes a second bulk acoustic waveresonator device including a second active region arranged betweenanother first electrode structure of the plurality of first electrodestructures and another second electrode structure of the plurality ofsecond electrode structures. In certain embodiments, the first andsecond bulk acoustic wave resonator devices are separable from oneanother, such as by dicing.

In another aspect, a bulk acoustic wave resonator chip is derived fromthe acoustic resonator structure. In another aspect, a sensor ormicrofluidic device incorporates the bulk acoustic wave resonator chip.In certain embodiments, a microfluidic device includes a channelarranged to permit a liquid to be introduced and arranged over theactive region of at least one bulk acoustic wave resonator chip.

In another aspect, a deposition system includes a first linearsputtering apparatus including a first target surface configured toeject metal atoms; a second linear sputtering apparatus including asecond target surface configured to eject metal atoms; a substrate tableincluding a support surface that is configured to receive at least onewafer and that is coupled to a translation element, wherein thetranslation element is configured to translate the substrate table andthe at least one wafer between a first position proximate to the firstlinear sputtering apparatus and a second position proximate to thesecond linear sputtering apparatus; and a second collimator including asecond plurality of guide members defining a second plurality ofcollimator apertures arranged between the second linear sputteringapparatus and the substrate table when the support surface is proximateto the second linear sputtering apparatus; wherein at least one of thefirst target surface or the second target surface is arrangednon-parallel to the support surface. In certain embodiments, thedeposition system further includes a first collimator including a firstplurality of guide members defining a first plurality of collimatorapertures arranged between the first linear sputtering apparatus and thesubstrate table when the support surface is proximate to the firstlinear sputtering apparatus.

In certain embodiments, the deposition system further includes a loadlock chamber, wherein the translation element is configured to translatethe substrate table and the at least one wafer from the load lockchamber to at least one of the first position or the second position. Incertain embodiments, the deposition system further includes an enclosurecontaining the first linear sputtering apparatus, the second linearsputtering apparatus, the second collimator, and the substrate table;and at least one vacuum pumping element configured to generate at leastone subatmospheric pressure condition within the enclosure.

In certain embodiments, the deposition system further includes a firstvacuum pumping element configured to generate a first subatmosphericpressure condition in a first chamber containing the first linearsputtering apparatus, and including a second vacuum pumping elementconfigured to generate a second subatmospheric pressure condition in asecond chamber containing the second linear sputtering apparatus. Incertain embodiments, the first chamber further includes a firstdeposition aperture (optionally in combination with a first collimator),and the second chamber further includes the second collimator and asecond deposition aperture, wherein the substrate table is capable ofbeing moved between the first chamber and the second chamber.

In certain embodiments, at least one of the first plurality of guidemembers or the second plurality of guide members is arrangednon-perpendicular to the support surface. In certain embodiments, thesecond plurality of guide members includes a second plurality oflongitudinal members and a second plurality of transverse members thatform a second grid. If provided, the first plurality of guide members incertain embodiments includes a first plurality of longitudinal membersand a second plurality of transverse members that form a first grid.

In certain embodiments, the substrate table is electrically biased to apotential other than ground. In certain embodiments, at least one of thefirst collimator or the second collimator is electrically biased to apotential other than ground.

In certain embodiments, the first linear sputtering apparatus includes afirst linear magnetron that includes a first sputtering cathodeoperatively coupled to the first target surface to promote ejection ofmetal atoms from the first target surface, and wherein the second linearsputtering apparatus includes a second linear magnetron that includes asecond sputtering cathode operatively coupled to the second targetsurface to promote ejection of metal atoms from the second targetsurface. In certain embodiments, the first collimator (if provided) isconfigured to translate during operation of the first linear sputteringapparatus, and the second collimator is configured to translate duringoperation of the second linear sputtering apparatus.

In certain embodiments, the deposition system further includes anenclosure containing the first chamber and the second chamber. In suchan embodiment, the second growth step using the second collimator may beperformed in a sequential manner in a subatmospheric environmentfollowing the first growth step using the first collimator without anyneed for removing a substrate or resonator device complex into anatmospheric pressure environment before the second growth step (e.g.,which would otherwise require significant time and energy to establishsubatmospheric conditions in the second chamber).

In certain embodiments, the second target surface is oriented 15 to 55degrees apart from the support surface. In certain embodiments, thesupport surface is configured to receive at least two wafers each havinga diameter of at least 50 mm (or at least 100 mm, or at least 150 mm).In certain embodiments, each of the first target surface and the secondtarget surface includes aluminum and is configured to eject aluminumatoms, such as may be useful to produce aluminum nitride. In certainembodiments, each of the first target surface and the second targetsurface includes zinc and is configured to eject zinc atoms, such as maybe useful to produce zinc oxide.

In certain embodiments, the deposition system is configured to receive asupply of sputtering gas, wherein the sputtering gas includes a gasspecies adapted to react with the metal atoms. In certain embodiments,the gas species includes nitrogen or oxygen, optionally in combinationwith one or more other gas constituents, such as (but not limited to)argon or other noble gases.

In certain embodiments, the deposition system includes at least onewafer received by the support surface, wherein an acoustic reflectorstructure is arranged over the at least one wafer, and at least oneelectrode structure is arranged over at least a portion of the acousticreflector structure.

In certain embodiments, the deposition system includes at least onewafer received by the support surface, wherein the at least one wafercomprises a substrate defining a recess, a support layer is arrangedover the recess, and an electrode structure is arranged over the supportlayer.

In certain embodiments, the deposition system further includes a firstdeposition aperture arranged between the first collimator and thesubstrate table; a first uniformity shield configured to permitadjustment of dimensions of the first deposition aperture; a seconddeposition aperture arranged between the second collimator and thesubstrate table; and a second uniformity shield configured to permitadjustment of dimensions of the second deposition aperture.

In certain embodiments, the first linear sputtering apparatus,optionally in conjunction with the first collimator, is configured forgrowth of a crystalline seed layer over the at least one wafer, thecrystalline seed layer including a c-axis having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the at least one wafer; and the secondlinear sputtering apparatus and the second collimator are configured forgrowth of a hexagonal crystal structure piezoelectric material bulklayer over the crystalline seed layer, the hexagonal crystal structurepiezoelectric material bulk layer including a c-axis having anorientation distribution predominantly in a range of from 30 degrees to50 degrees relative to normal of a face of the at least one wafer.

In certain embodiments, the support surface is configured to receive theat least one wafer, said at least one wafer having a diameter of atleast 50 mm (or at least 100 mm, or at least 150 mm); the first linearsputtering apparatus, optionally in conjunction with the firstcollimator, is configured for growth of the crystalline seed layercovering at least about 50% (or at least about 75%, or at least about90%, or at least about 95%) of a face of the at least one wafer; and thesecond linear sputtering apparatus and the second collimator areconfigured for growth of the hexagonal crystal structure piezoelectricmaterial bulk layer covering at least about 50% (or at least about 75%,or at least about 90%, or at least about 95%) of a face of the at leastone wafer.

In another aspect, a method for fabricating at least one resonatorstructure includes moving at least one wafer structure supported by asubstrate table to a first station containing a first linear sputteringapparatus that includes a first target surface configured to eject metalatoms; generating a first subatmospheric pressure condition at the firststation; performing a first growth step including ejection of metalatoms from the first target surface to (i) transit through a firstdeposition aperture (optionally preceded by transit through a firstcollimator including multiple first collimator apertures), and (ii)react with a gas species and be received by the at least one waferstructure, to deposit a crystalline seed layer over the at least onewafer structure; moving the at least one wafer structure supported bythe substrate table to a second station containing a second linearsputtering apparatus that includes a second target surface configured toeject metal atoms; generating a second subatmospheric pressure conditionat the second station; and performing a second growth step includingejection of metal atoms from the second target surface to (i) transitthrough a second collimator including multiple second collimatorapertures and through a second deposition aperture, and (ii) react witha gas species and be received by the at least one wafer structure, todeposit a hexagonal crystal structure piezoelectric material bulk layerover the crystalline seed layer that is arranged over the at least onewafer structure; wherein the hexagonal crystal structure piezoelectricmaterial bulk layer includes a c-axis orientation distribution thatdiffers from a c-axis orientation distribution of the crystalline seedlayer.

In certain embodiments, the second growth step is configured to yield atleast 50% (or at least about 75%, or at least about 90%, or at leastabout 95%) of the hexagonal crystal structure piezoelectric materialbulk layer including a c-axis having an orientation distributionpredominantly in a range of from 25 degrees to 50 degrees (or in asubrange of from 30 degrees to 40 degrees) relative to normal of a faceof the at least one wafer structure.

In certain embodiments, the first growth step is configured to yield atleast 50% (or at least about 75%, or at least about 90%, or at leastabout 95%) of the crystalline seed layer having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the at least one wafer structure.

In certain embodiments, the method further includes loading thesubstrate table supporting the at least one wafer structure into a loadlock chamber, and generating an initial subatmospheric condition in theload lock chamber, prior to the moving of the at least one waferstructure supported by the substrate table to the first station.

In certain embodiments, the first station and the second station arearranged within a single enclosure in which the first subatmosphericpressure condition and the second subatmospheric pressure condition aregenerated. In certain embodiments, a pressure of the firstsubatmospheric pressure condition is greater than a pressure of thesecond subatmospheric pressure condition. In certain embodiments, thefirst station is arranged within a first chamber, and the second stationis arranged within a second chamber.

In certain embodiments, the first growth step is performed at adeposition pressure in a range of from about 5 mT to about 50 mT. Incertain embodiments, the first growth step includes translating thefirst collimator during deposition of the crystalline seed layer overthe at least one wafer structure, and the second growth step includestranslating the second collimator during deposition of the hexagonalcrystal structure piezoelectric material bulk layer over the crystallineseed layer. In certain embodiments, the first growth step includestranslating the substrate table supporting the at least one waferstructure during deposition of the crystalline seed layer over the atleast one wafer structure, and the second growth step includestranslating the substrate table supporting the at least one waferstructure during deposition of the hexagonal crystal structurepiezoelectric material bulk layer over the crystalline seed layer.

In certain embodiments, the second target surface is oriented 15 to 55degrees apart from a face of the at least one wafer structure.

In certain embodiments, each wafer structure of the at least one waferstructure includes a substrate and at least one first electrodestructure arranged over at least a portion of the substrate.

In certain embodiments, each wafer structure of the at least one waferstructure includes a substrate, at least one acoustic reflectorstructure arranged over the substrate, and at least one first electrodestructure arranged over at least a portion of the at least one acousticreflector structure. In certain embodiments, each wafer structure of theat least one wafer structure includes a substrate defining a recess, asupport layer arranged over the recess, and at least one first electrodestructure arranged over the support layer.

In certain embodiments, each wafer structure of the at least one waferstructure includes a diameter of at least about 50 mm (or at least about100 mm, or at least about 150 mm), and the hexagonal crystal structurepiezoelectric material bulk layer covers at least about 50% (or at leastabout 75%, or at least about 90%, or at least about 95%) of a face ofthe at least one wafer structure.

In certain embodiments, the at least one wafer structure includes aplurality of wafer structures.

In certain embodiments, the crystalline seed layer is compositionallymatched to the hexagonal crystal structure piezoelectric material bulklayer. In certain embodiments, the hexagonal crystal structurepiezoelectric material bulk layer includes aluminum nitride or zincoxide. In certain embodiments, other hexagonal crystal structurepiezoelectric materials may be used.

In certain embodiments, the method further includes forming at least onesecond electrode structure over at least one portion of the hexagonalcrystal structure piezoelectric material bulk layer. In certainembodiments, the method further includes electrically biasing to apotential other than ground one or more of the following items: thesubstrate table, the first collimator, or the second collimator. Incertain embodiments, the method further includes roughening a backsideof the substrate after said forming of the at least one second electrodestructure.

In certain embodiments, the method further includes dicing the at leastone wafer structure, over which the hexagonal crystal structurepiezoelectric material bulk layer and the crystalline seed layer aredeposited, into a plurality of chips. In certain embodiments, each chipof the plurality of chips includes a solidly mounted bulk acoustic waveresonator chip or a film bulk acoustic wave resonator chip.

Those skilled in the art will appreciate the scope of the presentdisclosure and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified schematic of an axial sputtering depositionapparatus arranged to eject metal atoms from a target surface toward asubstrate supported by a substrate holder substantially parallel to thetarget surface, with central axes of the target surface and thesubstrate being aligned with one another.

FIG. 2A is a schematic representation of a rocking curve measurementgeometry of an AlN film structure obtained by radio frequency magnetronsputtering in a reactive gas environment in a planar sputtering systemwithout tilting the substrate, showing zero tilt angle at the center,and a radially symmetrical variation of tilt angle of crystallites inthe AlN film structure.

FIG. 2B is a plot of tilt angle versus distance from center for the AlNfilm structure described in connection with FIG. 2A, showing a nearlylinear variation of tilt angle with increasing distance away from acenter of the AlN film structure.

FIG. 3 is a plot of shear coupling coefficient (K_(s)) and longitudinalcoupling coefficient (K_(l)) as a function of c-axis angle ofinclination for AlN.

FIG. 4A is a simplified schematic of an off-axis sputtering depositionapparatus arranged to eject metal atoms from a target surface toward asubstrate supported by a substrate holder substantially parallel to thetarget surface, with central axes of the substrate and the targetsurface being parallel but offset relative to one another.

FIG. 4B is a simplified schematic of a sputtering deposition apparatusarranged to eject metal atoms from a target surface toward a substratesupported by a substrate holder that is non-parallel to the targetsurface, with a central axis of the target surface extending through acenter point of the substrate.

FIG. 4C is a simplified schematic of a sputtering deposition apparatusarranged to eject metal atoms from a target surface toward a substratesupported by a substrate holder that is non-parallel to the targetsurface, with a central axis of the substrate extending through a centerpoint of the target surface, and with a central axis of the targetsurface being separated from the central axis of the substrate by afirst angle, and with the substrate holder being tilted by a secondangle relative to a plane parallel with the target surface.

FIG. 5A is a cross-sectional schematic view of a seed layer exhibitingmultiple textures (e.g., (103) and (002)) deposited via a firstsputtering step over a substrate.

FIG. 5B is a cross-sectional schematic view of the seed layer andsubstrate of FIG. 5A following deposition via a second sputtering stepof a tilted axis AlN film over the seed layer.

FIG. 6 is a schematic cross-sectional view of a portion of a bulkacoustic wave solidly mounted resonator device including an inclinedc-axis hexagonal crystal structure piezoelectric material bulk layer asdisclosed herein, with the resonator device including an active regionwith a portion of the piezoelectric material arranged betweenoverlapping portions of a top side electrode and a bottom sideelectrode.

FIG. 7 is a schematic cross-sectional view of a portion of a bulkacoustic wave solidly mounted resonator device according to oneembodiment including an inclined c-axis hexagonal crystal structurepiezoelectric material bulk layer arranged over a crystalline seed layeras disclosed herein, with the resonator device including an activeregion with a portion of the piezoelectric material arranged betweenoverlapping portions of a top side electrode and a bottom sideelectrode.

FIG. 8 is a schematic cross-sectional view of a film bulk acoustic waveresonator (FBAR) device according to one embodiment including aninclined c-axis hexagonal crystal structure piezoelectric material bulklayer arranged over a crystalline seed layer as disclosed herein, withthe FBAR device including a substrate defining a cavity covered by asupport layer, and including an active region registered with the cavitywith a portion of the piezoelectric material arranged betweenoverlapping portions of a top side electrode and a bottom sideelectrode.

FIG. 9 is an upper exterior perspective view of a reactor of adeposition system for growing a hexagonal crystal structurepiezoelectric material with an inclined c-axis, the system including alinear sputtering apparatus, a movable substrate table for supportingmultiple substrates, and a collimator, according to one embodiment ofthe present disclosure.

FIG. 10 is a downwardly-facing cross-sectional view of the reactor ofFIG. 9.

FIG. 11 is a downwardly-facing cross-sectional view of a portion of thereactor of FIGS. 9 and 10, showing a cathode and target surface of thelinear sputtering apparatus, the collimator, and a deposition apertureincluding a uniformity shield.

FIG. 12 is an upper perspective view of a portion of the reactor ofFIGS. 9 and 10, showing the target surface of the linear sputteringapparatus, the collimator, and the deposition aperture, and theflange-terminated translation section including rails for supporting amovable substrate table.

FIG. 13 is an upper perspective view of a portion of the reactor ofFIGS. 9 and 10, showing the target surface of the linear sputteringapparatus, the collimator, and the deposition aperture, and a portion ofthe flange-terminated translation section for supporting a movablesubstrate table.

FIG. 14A is a side elevation view of a portion of the reactor of FIGS. 9and 10, showing a rear portion of the flange-terminated translationsection, and showing the movable substrate table (in dashed lines)supporting two substrates (also in dashed lines), with the movablesubstrate table in a first position.

FIG. 14B is a side elevation view of the reactor portion shown in FIG.14A, with the movable substrate table and substrates (in hidden lines)in a second position.

FIG. 15A is a side elevation view of the substrate table shown in FIGS.13, 14A, and 14B, with the substrate table supporting two roundsubstrates.

FIG. 15B is a side elevation view of the substrate table shown in FIGS.14A, 14B, and 15A, with the substrate table supporting four roundsubstrates.

FIG. 16 is a rear perspective view of a translation section for usewithin the reactor of FIGS. 9 and 10, including translation rails, amovable truck, and a drive screw assembly, as well as substrate tablebiasing hardware in a disengaged configuration.

FIG. 17 is a magnified rear perspective view of the translation sectionof FIG. 16 with the substrate table biasing hardware in an engagedconfiguration.

FIG. 18 is a perspective assembly view of a portion of the translationsection of FIGS. 16 and 17, showing translation rails arranged betweenchamber adapters, and showing sputter shields prior to attachment to therails.

FIG. 19 is a perspective view of a portion of the reactor of FIGS. 9 and10, including a collimator, collimator motion guide rails, and ascrew-type drive mechanism for causing the translation of thecollimator.

FIG. 20 is a perspective assembly view of at least a portion of thecollimator shown in FIG. 19.

FIG. 21 is a simplified schematic showing electrical connections tocollimator and target surface portions of a reactor according to FIGS. 9and10 according to one embodiment, including independent electricalcontrol of different collimator guides.

FIG. 22 is a top plan view of a portion of the reactor of FIGS. 9 and 10visible through an upper cathode flange, showing a deposition aperture,uniformity shield, cathode, target surface, and collimator, with thecollimator and the target surface in a first configuration.

FIG. 23 is a top plan view of the reactor portion of FIG. 22, with thecollimator and cathode assembly in a second configuration.

FIG. 24 is a cross-sectional view of a portion of the reactor of FIGS. 9and 10, showing the cathode assembly, target surface, and collimator.

FIG. 25 is a perspective cross-sectional view of a portion of thecathode assembly shown in FIG. 24 and useable in the reactor of FIGS. 9and 10.

FIG. 26 is a perspective view of a cathode magnet structure of thecathode assembly portion in FIG. 25.

FIG. 27 is a perspective view of a cathode assembly including theportion of FIG. 25 and the cathode magnet structure of FIG. 26.

FIG. 28 is a perspective view of an alternative collimator assemblyarranged within a deposition reactor, with vertical guide membersextending in a single direction and with wiring permitting individualelectrical biasing of each vertical guide member.

FIG. 29A is a plot of bias voltage versus time for an electricallybiased collimator, including oscillations due to translation of thecollimator.

FIG. 29B is a plot of bias voltage versus time embodying a magnifiedportion of the plot of FIG. 29A for time values of 65 minutes to 75minutes.

FIG. 30A is a schematic diagram showing components and pipingconnections of a deposition system including multiple linear sputteringapparatuses, a translatable substrate table, and multiple collimatorsarranged between the substrate table and the respective linearsputtering apparatuses.

FIG. 30B is a schematic diagram showing components, including thermaland control components, of the deposition system of FIG. 30A.

FIG. 31 is a plot of intensity versus c-axis angle for X-ray diffractionanalysis of a tilted c-axis AlN bulk layer formed over a substratewithout an intervening seed layer.

FIG. 32 is a plot of intensity versus c-axis angle for X-ray diffractionanalysis of a tilted c-axis AlN bulk layer formed over an AlN seed layersupported by a substrate, with the seed layer formed at a comparativelylow pressure of 5 mT.

FIG. 33 is a plot of intensity versus c-axis angle for X-ray diffractionanalysis of a tilted c-axis AlN bulk layer formed over an AlN seed layersupported by a substrate, with the seed layer formed at a comparativelyhigher pressure of 15 mT.

FIG. 34 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) versus c-axis angleof inclination for AlN.

FIG. 35 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) for a first set ofeight AlN film samples grown according to three growth conditions (i.e.,no seed layer, seed layer grown at 5 mT, and seed layer grown at 15 mT).

FIG. 36 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) for a second set oftwenty-four AlN film samples grown according to three growth conditions(i.e., no seed layer (five samples), seed layer grown at 5 mT (fourteensamples), and seed layer grown at 15 mT (five samples)).

FIG. 37A is a cross-sectional scanning electrode microscopy (SEM)photograph (50,000× magnification) of an AlN bulk layer deposited overan AlN seed layer grown at 5 mT.

FIG. 37B is a SEM photograph (50,000× magnification) of a top surface ofthe AlN bulk layer of FIG. 37A.

FIG. 38A is a cross-sectional view SEM photograph (50,000×magnification) of an AlN bulk layer deposited over an AlN seed layergrown at 15 mT.

FIG. 38B is a SEM photograph (50,000× magnification) of a top surface ofthe AlN bulk layer of FIG. 38A.

FIG. 39 is a cross-sectional view SEM photograph (50,000× magnification)of an AlN bulk layer having a c-axis tilted 35 degrees relative tonormal of an underlying substrate.

FIG. 40A is a cross-sectional SEM photograph (50,000× magnification) ofa portion of an AlN bulk layer grown without the use of an AlN seedlayer and without the use of collimator biasing.

FIG. 40B is a cross-sectional SEM photograph (75,000× magnification) ofa portion of the same film of FIG. 40A with an AlN bulk layer grownwithout the use of an AlN seed layer and without the use of collimatorbiasing, wherein the AlN bulk layer exhibits a c-axis tilt angle of 9.63degrees relative to normal of a substrate.

FIG. 41A is a cross-sectional SEM photograph (50,000× magnification) ofa portion of an AlN bulk layer grown without the use of an AlN seedlayer but with the use of collimator biasing.

FIG. 41B is a cross-sectional SEM photograph (75,000× magnification) ofa portion of the same film of FIG. 41A with an AlN bulk layer grownwithout the use of an AlN seed layer but with use of collimator biasing,wherein the AlN bulk layer exhibits a c-axis tilt angle of 6.83 degreesrelative to normal of a substrate.

DETAILED DESCRIPTION

Embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer, or region to another element, layer, or region asillustrated in the Figures. It will be understood that these terms andthose discussed above are intended to encompass different orientationsof the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” and/or “including” when used herein specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the terms “proximate”and “adjacent” as applied to a specified layer or element refer to astate of being close or near to another layer or element, and encompassthe possible presence of one or more intervening layers or elementswithout necessarily requiring the specified layer or element to bedirectly on or directly in contact with the other layer or elementunless specified to the contrary herein.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

The present disclosure relates in various aspects to bulk acoustic waveresonator structures, methods for fabricating such resonator structures,and deposition systems suitable for producing inclined c-axis hexagonalcrystal structure piezoelectric material that may be incorporated insuch resonator structures. As compared to conventional resonatorstructures, fabrication methods, and deposition systems, variousembodiments disclosed herein include or enable inclined c-axispiezoelectric films to be fabricated over large areas (e.g., large areasubstrates) with increased uniformity of c-axis tilt angle, preferablyaccompanied with c-axis tilt angles of sufficient magnitude to provide ashear coupling coefficient exceeding a longitudinal couplingcoefficient.

Various factors are used separately or in combination in one or moreembodiments to enable efficient growth of inclined c-axis hexagonalcrystal structure piezoelectric material of uniform character over largeareas. One factor includes use of a deposition system incorporating amulti-aperture collimator arranged between a target surface of a linearsputtering apparatus and a substrate table that supports one or morewafers or substrates for receiving sputter-deposited material (with thetarget surface being non-parallel to the substrate table, and theintermediately arranged collimator preferably being non-parallel toboth), wherein the collimator and the substrate table are preferablyboth capable of movement (e.g., translation) during sputtering, and atleast one of the substrate table or the collimator is preferably biasedto an electrical potential other than ground. Another factor includesgrowth of a crystalline seed layer during a first step according to afirst set of process conditions, followed by growth of a hexagonalcrystal structure piezoelectric material bulk layer (of a defined c-axisdistribution range) over the crystalline seed layer during a second stepaccording to a second set of process conditions (e.g., at a higherpressure than used during the first growth step and/or using a targetsurface and collimator that are angled differently relative to asubstrate or wafer in different growth steps). Such growth steps may beperformed using a single sputtering apparatus in certain embodiments. Inother embodiments, such growth steps may be performed with a depositionsystem utilizing multiple linear sputtering apparatuses, a substratetable that is translatable between different positions proximate todifferent linear sputtering apparatuses, and multiple collimatorsarranged between the substrate table and the respective linearsputtering apparatuses. For example, a crystalline seed layer may begrown by reactive sputtering at a first station using a first collimatoraccording to a first growth step, and a hexagonal crystal structurepiezoelectric material bulk layer comprising a different c-axisorientation distribution than the crystalline seed layer may be grown byreactive sputtering at a second station using a second collimatoraccording to a second growth step, wherein both stations are located ina single enclosure in which subatmospheric conditions may be generatedusing at least one vacuum pumping element, and a wafer or substratesupporting the respective layers may be moved between the stationswithout need for removal from subatmospheric conditions. In certainembodiments, the first collimator may be omitted for growth of thecrystalline seed layer. In certain embodiments, the first station isarranged within a first chamber and the second station is arrangedwithin a second chamber, wherein at least one first vacuum pumpingelement is associated with the first chamber and at least one secondvacuum pumping element is associated with the second chamber. In certainembodiments, different process conditions and/or different angularpositions between target surfaces, collimators, and a wafer or supportsurface may be used in the first and second growth steps. For example, afirst growth step may be configured to yield at least 50% (or at least75%, or at least 90%, or at least 95%) of the crystalline seed layerincluding a c-axis having an orientation distribution predominantly in arange of from 0 degrees to 35 degrees relative to normal of a face ofthe substrate or wafer, and a second growth step may be configured toyield at least 50% (or at least 75%, or at least 90%, or at least 95%)of the hexagonal crystal structure piezoelectric material bulk layerincluding a c-axis having an orientation distribution predominantly in arange of from 25 degrees to 50 degrees (or in a subrange of from 30degrees to 40 degrees) relative to normal of a face of the substrate orwafer. In certain embodiments, sputtering pressure during deposition ofa hexagonal crystal structure piezoelectric material bulk layer such asAlN may be in a range of from 0.7 to 3 mTorr (mT) to obtain adequate AlNc-axis (002) orientation.

In one aspect of the present disclosure, a deposition system suitablefor growing tilted c-axis hexagonal crystal structure piezoelectricmaterial includes a linear sputtering apparatus, a multi-aperturecollimator, and a translatable substrate table having a support surfacearranged non-parallel to a target surface of the sputtering apparatus,with the substrate table and/or the collimator being electrically biasedto a potential other than ground. The linear sputtering apparatus, whichmay include a linear magnetron or a linear ion beam sputteringapparatus, includes a target surface configured to eject metal (e.g.,aluminum or zinc) atoms, with the target surface being non-parallel to(e.g., oriented 15 to 55 degrees apart from) the support surface.Preferably, the collimator is also arranged non-parallel to the supportsurface. In certain embodiments, a target surface is arranged at a firstnonzero angle relative to a support surface, and a collimator isarranged at a second nonzero angle relative to the support surface,wherein the first nonzero angle is greater than the second nonzeroangle. Metal atoms ejected from the target surface react with a gasspecies contained in a gas-containing environment to form piezoelectricmaterial. For example, aluminum atoms ejected from an aluminum oraluminum-containing target surface may react with nitrogen gas speciesto form aluminum nitride, or zinc atoms ejected from a zinc orzinc-containing target surface may react with oxygen gas species to formzinc oxide.

In certain embodiments, a support surface of a substrate table isconfigured to receive at least one wafer (e.g., one, two, three, four,or more wafers, preferably having a diameter in a range of at leastabout 50 mm, about 100 mm, or about 150 mm) and is coupled to a movableelement (e.g., a translation element) configured to move the substratetable during operation of the linear sputtering apparatus, wherein suchmovement may promote uniform material deposition over large areas (e.g.,by preventing localized material deposition regions of differentthicknesses). An exemplary collimator includes multiple guide membersarranged non-parallel to the support surface, such as a plurality oflongitudinal members and a plurality of transverse members that form agrid defining multiple collimator apertures. Electrical biasing of thesubstrate table and/or the collimator to a potential other than groundenhances control of material deposition during operating of thesputtering apparatus. Collimator biasing has also been found toinfluence microstructure development of tilted c-axis piezoelectric bulkmaterial in a bulk acoustic wave resonator device. In certainembodiments, the substrate table and the collimator are independentlybiased to electrical potentials other than ground. In certainembodiments, different guide members of a collimator may be electricallybiased differently relative to one another. For example, in certainembodiments, a plurality of guide members includes a plurality oflongitudinal members biased to a first electrical potential other thanground and comprises a plurality of transverse members biased to asecond electrical potential other than ground, with the secondelectrical potential differing from the first electrical potential. Incertain embodiments, the collimator is configured to translate duringoperation of the linear sputtering apparatus, such as to preventformation of a “shadow” pattern that would otherwise be formed on asurface receiving deposited piezoelectric material following transit ofmetal atoms through the collimator. In certain embodiments, a depositionaperture (optionally augmented with a uniformity shield configured toadjust dimensions of the deposition aperture) is arranged between thecollimator and the substrate table.

In certain embodiments, a deposition system disclosed herein isconfigured for growth of a hexagonal crystal structure piezoelectricmaterial bulk layer over a crystalline seed layer (optionally beingcompositionally matched with the bulk layer) that overlies a waferreceived by the support surface, wherein at least 50% (or at least 75%,or at least 90%, or at least 95%) of the hexagonal crystal structurepiezoelectric material bulk layer comprises a c-axis having anorientation distribution predominantly in a range of from 25 degrees to50 degrees (or in a subrange of from 30 degrees to 40 degrees) relativeto normal of a face of a substrate or wafer received by the supportsurface. Such c-axis orientation distribution is preferablysubstantially uniform over the area of a large area substrate (e.g.,having a diameter in a range of at least about 50 mm, about 100 mm, orabout 150 mm), thereby enabling multiple chips having the same orsimilar acoustic wave propagation characteristics to be derived from asingle substrate. In certain embodiments, at least 50% (or at least 75%,or at least 90%, or at least 95%) of the crystalline seed layer includesa c-axis having an orientation distribution predominantly in a range offrom 0 degrees to 35 degrees relative to normal of a face of a substrateor wafer received by the support surface.

In certain embodiments, the deposition system includes at least onewafer received by the support surface, wherein the at least one wafercomprises a substrate, an acoustic reflector structure arranged over thesubstrate, and an electrode structure arranged over at least a portionof the acoustic reflector structure—such as may be useful to produce atleast one solidly mounted bulk acoustic wave resonator device. Incertain embodiments, the deposition system includes at least one waferreceived by the support surface, wherein the at least one wafercomprises a substrate defining a recess, a support layer is arrangedover the recess, and an electrode structure is arranged over the supportlayer—such as may be useful to produce at least one film bulk acousticwave resonator device.

In one aspect, the disclosure relates to a method for fabricating atleast one acoustic resonator structure, wherein a first growth stepincludes deposition of a crystalline seed layer over at least oneresonator device complex, and a second growth step includes depositionof a hexagonal crystal structure piezoelectric material bulk layer overthe crystalline seed layer (optionally, wherein the hexagonal crystalstructure piezoelectric material bulk layer is compositionally matchedto the crystalline seed layer). Each resonator device complex includes asubstrate and at least one first electrode structure arranged over atleast a portion of the substrate. The second growth step includesdeposition of a hexagonal crystal structure piezoelectric material bulklayer over the crystalline seed layer that is arranged over the at leastone resonator device complex, and is configured to yield at least 50%(or at least 75%, or at least 90%, or at least 95%) of the hexagonalcrystal structure piezoelectric material bulk layer including a c-axishaving an orientation distribution predominantly in a range of from 25degrees to 50 degrees (or in a subrange of from 30 degrees to 40degrees) relative to normal of a face of the substrate. At least one ofthe first growth step or the second growth step includes ejection ofmetal atoms from a target surface of a linear sputtering apparatus to(i) transit through a collimator including multiple collimator aperturesand through a deposition aperture, and (ii) react with a gas species andbe received by the at least one resonator device complex, wherein thetarget surface is arranged non-parallel to (e.g., in a range of 15 to 55degrees apart from) a face of the substrate. In certain embodiments, thefirst growth step is configured to yield at least 50% (or at least 75%,or at least 90%, or at least 95%) of the crystalline seed layercomprising a c-axis having an orientation distribution predominantly ina range of from 0 degrees to 35 degrees relative to normal of a face ofthe substrate. In certain embodiments, a first growth step is performedat a higher deposition pressure (e.g., in a range of from about 5 mT toabout 50 mT) than the second growth step. In certain embodiments, asubstrate table and/or collimator is configured to translate duringoperation of the linear sputtering apparatus, to promote uniformmaterial deposition. In certain embodiments, at least one secondelectrode structure is formed over at least one portion of the hexagonalcrystal structure piezoelectric material bulk layer, such as may beuseful to form at least one bulk acoustic wave resonator device. Anactive region of bulk acoustic wave resonator device is provided in anarea in which the hexagonal crystal structure piezoelectric materialbulk layer is arranged between a first electrode structure and a secondelectrode structure. Such growth steps may be performed using a singlesputtering apparatus in certain embodiments. In other embodiments, suchgrowth steps may be performed with a deposition system utilizingmultiple linear sputtering apparatuses, a substrate table that istranslatable between different positions proximate to different linearsputtering apparatuses, and multiple collimators arranged between thesubstrate table and the respective linear sputtering apparatuses. Incertain embodiments, at least one resonator device complex, over whichthe hexagonal crystal structure piezoelectric material bulk layer andthe crystalline seed layer are deposited, is diced into a plurality ofchips, such as solidly mounted bulk acoustic wave resonator chips orfilm bulk acoustic wave resonator chips.

Although various embodiments disclosed herein are directed to use oflinear sputtering apparatuses, in alternative embodiments, one or morerotating sputtering apparatuses such as rotating magnetrons may besubstituted.

In one aspect of the present disclosure, an acoustic resonator structureinclude a substrate supporting at least one first electrode, acrystalline seed layer arranged over the at least one first electrode, ahexagonal crystal structure piezoelectric material bulk layer(optionally compositionally matched with the crystalline seed layer)arranged over the crystalline seed layer, and at least one secondelectrode structure arranged over at least a portion of the hexagonalcrystal structure piezoelectric material bulk layer, wherein at least50% (or at least 75%, or at least 90%, or at least 95%) of the hexagonalcrystal structure piezoelectric material bulk layer comprises a c-axishaving an orientation distribution predominantly in a range of from 25degrees to 50 degrees (or in a subrange of from 30 to 40 degrees)relative to normal of a face of the substrate. In certain embodiments, athickness of the crystalline seed layer is no greater than about 20%, nogreater than about 15%, or no greater than about 10% of a combinedthickness of the hexagonal crystal structure piezoelectric material bulklayer and the crystalline seed layer. In certain embodiments, thecrystalline seed layer may comprise a thickness in a range of from about500 to about 2,000 Angstroms and/or the hexagonal crystal structurepiezoelectric material bulk layer may comprise a thickness in a range offrom about 4,000 to about 26,000 Angstroms. In certain embodiments, atleast 50% (or at least 75%, or at least 90%, or at least 95%) of thecrystalline seed layer comprises a c-axis having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the substrate. In certain embodiments,an acoustic reflector structure is arranged between the substrate andthe at least one first electrode structure to provide a solidly mountedbulk acoustic resonator device. Optionally, a backside of the substratemay include a roughened surface configured to reduce or eliminatebackside acoustic reflection. In other embodiments, the substratedefines a recess, a support layer is arranged over the recess, and thesupport layer is arranged between the substrate and at least a portionof the at least one first electrode structure, to provide a film bulkacoustic wave resonator structure. In certain embodiments, less thanabout 3 percent of the c-axis orientation distribution of the hexagonalcrystal structure piezoelectric material bulk layer is in a range offrom 0 degrees to 15 degrees relative to normal of a face of thesubstrate. In certain embodiments, the substrate comprises a diameter ofat least about 50 mm (or at least about 100 mm, or at least about 150mm) and the hexagonal crystal structure piezoelectric material bulklayer covers at least about 50% (or at least about 75%, or at leastabout 90%, or at least about 95%) of a face of the substrate. In certainembodiments, multiple bulk acoustic wave resonator devices eachincluding an active region between a first electrode structure and asecond electrode structure are provided on a single substrate. Multiplebulk acoustic resonator chips may be derived from such a substrate(e.g., by dicing), and may be incorporated in one or more sensors and/orfluidic devices.

In one aspect of the present disclosure, a deposition system includesfirst and second linear sputtering apparatuses (e.g., linear magnetronor linear ion beam sputtering apparatuses) and a translation elementconfigured to translate a substrate table that is configured to receiveat least one wafer between a first position proximate to the firstlinear sputtering apparatus and a second position proximate to thesecond linear sputtering apparatus. Such a system may be used, forexample, to perform a second growth step in a sequential manner in asubatmospheric environment following performance of a first growth stepwithout a need to remove a wafer or substrate into an atmosphericpressure environment before the second growth step (e.g., which wouldotherwise require significant time and energy to establishsubatmospheric conditions in the second chamber). The first linearsputtering apparatus includes a first target surface, and the secondlinear sputtering apparatus including a second target surface, whereineach target surface is configured to eject metal atoms. A firstcollimator (if provided) includes a first plurality of guide membersthat define a first plurality of collimator apertures arranged betweenthe first linear sputtering apparatus and the substrate table when thesupport surface is proximate to the first linear sputtering apparatus,and a second collimator includes a second plurality of guide membersthat defines a second plurality of collimator apertures arranged betweenthe second linear sputtering apparatus and the substrate table when thesupport surface is proximate to the second linear sputtering apparatus.In certain embodiments, the first collimator may be omitted. In certainembodiments, the first and/or the second collimator includes a pluralityof longitudinal members and a plurality of transverse members that forma grid. At least one (or both) of the first target surface or the secondtarget surface is arranged non-parallel to a support surface of thesubstrate table. In certain embodiments, a load lock chamber isprovided, wherein a translation element is configured to translate thesubstrate table and the at least one wafer from the load lock chamber toa first position (e.g., at a first station) proximate to the firstlinear sputtering apparatus, and is further configured to translate thesubstrate table and the at least one wafer to a second position (e.g.,at a second station) proximate to the second linear sputteringapparatus. In certain embodiments, an enclosure contains the firststation (e.g., including the first linear sputtering apparatus, a first(optional) collimator, and a first deposition aperture) and contains thesecond station (e.g., including the first linear sputtering apparatus, afirst (optional) collimator, and a first deposition aperture), whereinat least one vacuum pumping element is configured to generate at leastone subatmospheric pressure condition within the enclosure In certainembodiments, the first station may be contained in a first chamber, andthe second station may be contained in a second chamber. For example, incertain embodiments, first and second vacuum pumping elements areconfigured to generate first and second subatmospheric pressureconditions, respectively, in a first chamber containing the first linearsputtering apparatus and in a second chamber containing the secondlinear sputtering apparatus, wherein both chambers may be located in anenclosure. In certain embodiments, first and second depositionapertures, each including an associated uniformity shield configured topermit adjustment of dimensions of the deposition aperture, arepositioned between respective collimators and the substrate table.

In certain embodiments, the first linear sputtering apparatus,optionally in combination with a first collimator, is configured forgrowth of a crystalline seed layer over the at least one wafer, thecrystalline seed layer comprising a c-axis having an orientationdistribution predominantly in a range of from 0 degrees to 35 degreesrelative to normal of a face of the at least one wafer. It is to berecognized that a crystalline seed layer having a c-axis orientationdistribution of 0 degrees may be attained without a first collimator,and that even (non-zero) shallow angle c-axis orientation distributionsmay be attained without a first collimator (e.g., if a first targetsurface is sufficiently angled relative to a surface of the at least onewafer); however, more uniform and/or more steeply angled (non-zero)c-axis orientation distributions may be promoted with use of a firstcollimator as disclosed herein. Additionally, the second linearsputtering apparatus and the second collimator are configured for growthof a hexagonal crystal structure piezoelectric material bulk layer overthe crystalline seed layer, the hexagonal crystal structurepiezoelectric material bulk layer comprising a c-axis having anorientation distribution predominantly in a range of from 30 degrees to50 degrees (or in a subrange of from 30 degrees to 40 degrees) relativeto normal of a face of the at least one wafer. In certain embodiments,the support surface is configured to receive at least one wafer having adiameter of at least about 50 mm (or at least about 100 mm, or at leastabout 150 mm), wherein the first linear sputtering apparatus, optionallyin combination with a first collimator, is configured for growth of thecrystalline seed layer covering at least about 50% (or at least about75%, or at least about 90%, or at least about 95%) of a face of the atleast one wafer, and the second linear sputtering apparatus and thesecond collimator are configured for growth of the hexagonal crystalstructure piezoelectric material bulk layer covering at least about 50%(or at least about 75%, or at least about 90%, or at least about 95%) ofa face of the at least one wafer. Preferably, each linear sputteringapparatus is configured to receive a supply of sputtering gas includinga gas species adapted to react with metal atoms ejected from a targetsurface, and in certain embodiments each target surface may comprisealuminum (e.g., to eject aluminum atoms that may react with nitrogenspecies to form AlN) or zinc (e.g., to eject zinc atoms that may reactwith oxygen species to form ZnO).

In another aspect of the present disclosure, a method for fabricating atleast one resonator structure includes use of a first station containinga first linear sputtering apparatus including a first target surface,and use of a second station containing a second linear sputteringapparatus including a second target surface. At least one waferstructure supported by a substrate table is moved to the first stationin which a first subatmospheric pressure condition is generated, a firstgrowth step is performed to deposit a crystalline seed layer over the atleast one wafer structure, the at least one wafer structure supported bythe substrate table is moved to the second station in which a secondsubatmospheric pressure is generated, and a second growth step isperformed to deposit a hexagonal crystal structure piezoelectricmaterial bulk layer over the crystalline seed layer, wherein thehexagonal crystal structure piezoelectric material bulk layer includes ac-axis orientation distribution that differs from a c-axis orientationdistribution of the crystalline seed layer. The first growth stepincludes ejection of metal atoms from the first target surface to (i)transit through a first deposition aperture (optionally preceded bytransit through a first collimator including multiple first collimatorapertures), and (ii) react with a gas species and be received by the atleast one wafer structure, to deposit the crystalline seed layer. Thesecond growth step includes ejection of metal atoms from the secondtarget surface to (i) transit through a second collimator includingmultiple second collimator apertures and through a second depositionaperture, and (ii) react with a gas species and be received by the atleast one wafer structure, to deposit the hexagonal crystal structurepiezoelectric material bulk layer. In certain embodiments, the firstgrowth step is configured to yield at least 50% (or at least about 75%,or at least about 90%, or at least about 95%) of the crystalline seedlayer having an orientation distribution predominantly in a range offrom 0 degrees to 35 degrees relative to normal of a face of the atleast one wafer structure; and the second growth step is configured toyield at least 50% (or at least about 75%, or at least about 90%, or atleast about 95%) of the hexagonal crystal structure piezoelectricmaterial bulk layer including a c-axis having an orientationdistribution predominantly in a range of from 25 degrees to 50 degrees(or in a subrange of from 30 degrees to 40 degrees) relative to normalof a face of the at least one wafer structure. In certain embodiments,the substrate table supporting the at least one wafer structure isloaded into a load lock chamber, and an initial subatmospheric conditionis generated in the load lock chamber, prior to the moving of the atleast one wafer structure supported by the substrate table to the firststation. In certain embodiments, the first station and the secondstation are arranged within a single enclosure in which the firstsubatmospheric pressure condition and the second subatmospheric pressurecondition are generated. In other embodiments, the first station isarranged within a first chamber having an associated first vacuumpumping element, and the second station is arranged within a secondchamber having an associated second vacuum pumping element.

In certain embodiments, a pressure of the first subatmospheric pressurecondition is greater than a pressure of the second subatmosphericpressure condition. In certain embodiments, the first growth step isperformed at a deposition pressure in a range of from about 5 mT toabout 50 mT. In certain embodiments, the first growth step optionallyincludes translating the first collimator during deposition of thecrystalline seed layer over the at least one wafer structure, and thesecond growth step includes translating the second collimator duringdeposition of the hexagonal crystal structure piezoelectric materialbulk layer over the crystalline seed layer. In certain embodiments, botha collimator and the substrate table are translated during materialdeposition to promote uniform deposition. A direction of translation ofthe collimator may be substantially perpendicular to a direction oftranslation of the substrate table; for example, a collimator may bemoved in a vertical direction while the substrate table is moved in ahorizontal direction. In certain embodiments, each wafer structure ofthe at least one wafer structure includes a diameter of at least about50 mm (or at least about 100 mm, or at least about 150 mm), and one ormore of the crystalline seed layer or the hexagonal crystal structurepiezoelectric material bulk layer covers at least about 50% (or at leastabout 75%, or at least about 90%, or at least about 95%) of a face ofthe at least one wafer structure. In certain embodiments, the at leastone wafer structure (over which the hexagonal crystal structurepiezoelectric material bulk layer and the crystalline seed layer aredeposited) is diced into a plurality of chips, wherein each chip mayinclude a solidly mounted bulk acoustic wave resonator chip or a filmbulk acoustic wave resonator chip.

In certain embodiments, linear sputtering apparatuses utilized hereinmay include linear magnetron-type sputtering apparatuses or linear ionbeam sputtering apparatuses. Ion beam deposition allows variable controlof primary (sputtering) and secondary (bombarding) ion beams, as well asthe potential for substrate manipulation, which may be beneficial topromote growth of hexagonal crystal structure piezoelectric material athigher c-axis tilt angles.

In certain embodiments, a hexagonal crystal structure piezoelectricmaterial bulk layer, which is deposited over a crystalline seed layer,comprises a c-axis having an orientation distribution predominantly in arange of from 12 degrees to 52 degrees, or in a range of from 27 degreesto 37 degrees, or in a range of from 75 degrees to 90 degrees, relativeto normal of a face of a substrate or wafer supporting the crystallineseed layer and hexagonal crystal structure piezoelectric material bulklayer. In certain embodiments, the hexagonal crystal structurepiezoelectric material bulk layer includes a thickness in a range offrom about 4,000 Angstroms to about 26,000 Angstroms. Such hexagonalcrystal structure piezoelectric material bulk layer preferably includessubstantially uniform thickness, nanostructure, and crystallinityproperties, with controlled stress and densely packed columnar grains orrecrystallized grain structure. In certain embodiments, a crystallineseed layer includes a thickness in a range of from 500 Angstroms to2,000 Angstroms, and (for a hexagonal crystal structure piezoelectricmaterial such as AlN) may include a dominant (103) texture.

Various aspects and features of the disclosure will be described withreference to the drawings, in which illustrated elements are not toscale unless specifically indicated to the contrary.

FIG. 6 is a schematic cross-sectional view of a portion of a bulkacoustic wave solidly mounted resonator device 50 including apiezoelectric material bulk layer 64 embodying an inclined c-axishexagonal crystal structure piezoelectric material (e.g., AlN or ZnO) asdisclosed herein. If the piezoelectric material bulk layer 64 comprisesAlN, then the (002) direction (or c-axis) is tilted away from adirection normal to a substrate 52, as illustrated by two arrowssuperimposed over the piezoelectric material bulk layer 64. Theresonator device 50 includes the substrate 52 (e.g., typically siliconor another semiconductor material), an acoustic reflector 54 arrangedover the substrate 52, the piezoelectric material bulk layer 64, andbottom and top side electrodes 60, 68. The bottom side electrode 60 isarranged between the acoustic reflector 54 and the piezoelectricmaterial bulk layer 64, and the top side electrode 68 is arranged alonga portion of an upper surface 66 of the piezoelectric material bulklayer 64. An area in which the piezoelectric material bulk layer 64 isarranged between overlapping portions of the top side electrode 68 andthe bottom side electrode 60 is considered the active region 70 of theresonator device 50. The acoustic reflector 54 serves to reflectacoustic waves and therefore reduce or avoid their dissipation in thesubstrate 52. In certain embodiments, the acoustic reflector 54 includesalternating thin layers 56, 58 of materials of different acousticimpedances (e.g., SiOC, Si₃N₄, SiO₂, AlN, and Mo), optionally embodiedin a Bragg mirror, deposited over the substrate 52. In certainembodiments, other types of acoustic reflectors may be used. Steps forforming the resonator device 50 may include depositing the acousticreflector 54 over the substrate 52, followed by deposition of the bottomside electrode 60, followed by growth (e.g., via sputtering or otherappropriate methods) of the piezoelectric material bulk layer 64,followed by deposition of the top side electrode 68.

FIG. 7 is schematic cross-sectional view of a portion of another bulkacoustic wave solidly mounted resonator device 50A including apiezoelectric material bulk layer 64 embodying an inclined c-axishexagonal crystal piezoelectric material (e.g., AlN or ZnO) arrangedover a crystalline seed layer 62. In certain embodiments, the inclinedc-axis hexagonal crystal piezoelectric material of the piezoelectricmaterial bulk layer 64 is compositionally matched to the crystallineseed layer 62. For example, the crystalline seed layer 62 may alsoembody AlN or ZnO. The resonator device 50A includes a substrate 52, anacoustic reflector 54 arranged over the substrate 52, a piezoelectricmaterial bulk layer 64, and bottom and top side electrodes 60, 68, withthe top side electrode 68 being arranged along a portion of an uppersurface 66 of the piezoelectric material bulk layer 64. A portion of thepiezoelectric material bulk layer 64 arranged between the top sideelectrode 68 and the bottom side electrode 60 embodies an active region70 of the bulk acoustic wave solidly mounted resonator device 50A. Stepsfor forming the resonator device 50A may include depositing the acousticreflector 54 over the substrate 52, followed by deposition of the bottomside electrode 60, followed by growth (e.g., via sputtering or otherappropriate methods) of the crystalline seed layer 62, growth of thepiezoelectric material bulk layer 64, and by deposition of the top sideelectrode 68.

FIG. 8 is a schematic cross-sectional view of a film bulk acoustic waveresonator (FBAR) device 72 according to one embodiment. The FBAR device72 includes a substrate 74 (e.g., silicon or another semiconductormaterial) defining a cavity 76 that is covered by a support layer 78(e.g., silicon dioxide). A bottom side electrode 80 is arranged over aportion of the support layer 78, with the bottom side electrode 80 andthe support layer 78 being overlaid with a crystalline seed layer 82. Apiezoelectric material bulk layer 84 embodying inclined c-axis hexagonalcrystal structure piezoelectric material (e.g., AlN or ZnO) is arrangedover the crystalline seed layer 82, and a top side electrode 88 isarranged over at least a portion of a top surface 86 of thepiezoelectric material bulk layer 84. A portion of the piezoelectricmaterial bulk layer 84 arranged between the top side electrode 88 andthe bottom side electrode 80 embodies an active region 90 of the FBARdevice 72. The active region 90 is arranged over and registered with thecavity 76 disposed below the support layer 78. The cavity 76 serves toconfine acoustic waves induced in the active region 90 by preventingdissipation of acoustic energy into the substrate 74, since acousticwaves do not efficiently propagate across the cavity 76. In thisrespect, the cavity 76 provides an alternative to the acoustic reflector54 illustrated in FIGS. 6 and 7. Although the cavity 76 shown in FIG. 8is bounded from below by a thinned portion of the substrate 74, inalternative embodiments at least a portion of the cavity 76 extendsthrough an entire thickness of the substrate 74. Steps for forming theFBAR device 72 may include defining the cavity 76 in the substrate 74,filling the cavity 76 with a sacrificial material (not shown) optionallyfollowed by planarization of the sacrificial material, depositing thesupport layer 78 over the substrate 74 and the sacrificial material,removing the sacrificial material (e.g., by flowing an etchant throughvertical openings defined in the substrate 74 or the support layer 78,or lateral edges of the substrate 74), depositing the bottom sideelectrode 80 over the support layer 78, growing (e.g., via sputtering orother appropriate methods) the crystalline seed layer 82 and thepiezoelectric material bulk layer 84, and depositing the top sideelectrode 88.

FIG. 9 is an upper exterior perspective view of a reactor 100 of adeposition system for growing a hexagonal crystal structurepiezoelectric material with an inclined c-axis, the system including alinear sputtering apparatus, a movable substrate table for supportingmultiple substrates, and a collimator, according to one embodiment ofthe present disclosure. The reactor 100 includes a first tubular portion102 extending in a generally vertical direction between a base 104 andan upper flange 106. Extending upward from the upper flange 106 is acollimator drive adapter flange 118 and a cylindrical high voltageshield 116, each including a central axis that is laterally offset froma central axis of the upper flange 106. A recirculating ball screw drivemechanism 114 and a collimator drive rotational seal 112 arranged tomate with a drive motor (not shown) further extend upward from thecylindrical high voltage shield 116. The purpose of the recirculatingball screw drive mechanism 114 and the collimator drive rotational seal112 are to facilitate movement (e.g., translation) of a collimatorassembly within the first tubular portion 102, as described in furtherdetail herein.

A medial section of the first tubular portion 102 is partially bisectedby a second tubular portion 120 extending in a generally horizontaldirection between a substrate translation flange 124 and a load lockattachment flange 134, with the second tubular portion 120 includinglower and upper substrate table translation rails. The substratetranslation flange 124 generally surrounds a first chamber adapter 122,which has a generally disc-like shape, includes a first aperture 126supporting a first end of a drive screw, and defines a rectangularaperture 130 generally aligned with a substrate table (not shown).Fasteners 128 are provided to attach drive screw supports (not shown)along an inner surface of the first chamber adapter 122. A third tubularportion 108 extends in a generally horizontal direction perpendicular tothe second tubular portion 120 and includes a flange 110 arranged tocouple to a vacuum pump (not shown) to generate a subatmosphericcondition within the reactor 100. A sputtering gas inlet port 125 isfurther arranged in fluid communication with the second tubular portion120 to admit a sputtering gas into the reactor 100.

FIG. 10 is a downwardly-facing cross-sectional view of the reactor 100of FIG. 9, showing the first, second, and third tubular portions 102,120, 108 as well as the substrate translation flange 124 and load lockattachment flange 134. A collimator assembly (“collimator”) 170 and alinear sputtering apparatus 154 (e.g., a pulsed direct current linearmagnetron cathode assembly) are provided within the first tubularportion 102 proximate to a deposition aperture 150 that is bounded alongone edge by a uniformity shield 152. The linear sputtering apparatus 154includes a target 166 including a surface configured to eject metalatoms, as well as a cathode body structure 156 with perimeter magnets238 and liquid cooling channels 158, arranged between channel guides 222extending in a vertical direction and arranged to receive collimatorsupport bearing assemblies (not shown) coupled to collimator sidebrackets 162. In certain embodiments, the target 166 includes dimensionsof about 5 inches by 16 inches. A collimator ground strap 168 is furtherarranged between the collimator assembly 170 and the linear sputteringapparatus 154. A translation section 115 enabling movement of asubstrate table 148 is arranged within the second tubular portion 120. Alower surface of the second tubular portion 120 supports a lowersubstrate table translation rail 142 defining a recess 144 for guidinglateral translation of movable trucks (not shown) that support thesubstrate table 148, with movement of the substrate table 148 duringoperation of the linear sputtering apparatus 154 beneficially promotinguniform deposition of sputtered material on one or more substrates (notshown) supported by the substrate table 148. As shown in FIG. 10, thetarget 166 is arranged at a first angle non-parallel to the substratetable 148, and the collimator assembly 170 is arranged between thetarget 166 and the substrate table 148 at a second angle non-parallel tothe substrate table 148, wherein the second angle is smaller than thefirst angle. During operation of the reactor 100, subatmosphericconditions are established with a vacuum pump (not shown) coupled to thethird tubular portion 108, and a sputtering gas is supplied to thereactor 100 through the sputtering gas inlet port 125 while metal atomsare ejected from a surface of the target 166 to transit through thecollimator assembly 170 toward one or more substrates supported by thesubstrate table 148. Reaction between the metal atoms (e.g., aluminum orzinc) and the sputtering gas (e.g., containing nitrogen or oxygen)yields molecules of piezoelectric material (e.g., AlN or ZnO) that aredeposited on or over one or more substrates (not shown).

FIG. 11 is a downwardly-facing cross-sectional view of a portion of thereactor of FIGS. 9 and 10, showing a substrate 214 arranged proximate tothe deposition aperture 150 (bounded in part by a shield panel 180 andthe uniformity shield 152), with the collimator assembly 170intermediately arranged between the substrate 214 and the linearsputtering apparatus 154. In certain embodiments, the depositionaperture 150 includes a width ranging from about 3 inches to about 9inches, with the uniformity shield 152 extending into the depositionaperture 150 including a maximum width of about 2 inches. The collimatorassembly 170 includes multiple horizontal guide members 172 and verticalguide members 174 that in combination form a grid defining multipleapertures that permit passage of metal atoms ejected by a surface of thetarget 166. The collimator assembly 170 is further bounded laterally bytubular supports 176. An ejection surface of the target 166 is arrangedalong a front surface of the linear sputtering apparatus 154, whichincludes liquid ports 164 configured to circulate liquid, and channelguides 222 arranged to receive bearings 160 and to support collimatorside brackets 162 that permit the collimator assembly 170 to move (e.g.,translate) in a vertical direction.

FIG. 12 is an upper perspective view of the translation section of thereactor of FIGS. 9 and 10, showing the collimator assembly 170 arrangedbetween the linear sputtering apparatus 154 and the deposition aperture150. The cathode body structure 156 includes a hollow interiorcontaining liquid cooling channels 158, with an ejection surface of thetarget 166 arranged along a front of the cathode body structure 156between the channel guides 222 that enable collimator side brackets 162supporting the collimator assembly 170 to translate in a verticaldirection. A collimator ground strap 168 extends between the linearsputtering apparatus 154 and the collimator assembly 170 along lowerportions thereof intermediately arranged between tubular supports 176bounding lateral edges of the collimator assembly 170. The depositionaperture 150 is bounded from above by an upper substrate tabletranslation rail 178, and laterally by shield panels 180, 182 as well asa uniformity shield 152 (optionally including multiple finger portionsof different lengths) that extends laterally from one shield panel 182,which may be repositioned by sliding laterally within a secondary slot(not shown) defined in a lower substrate table translation rail 142(which also defines a recess 144 for guiding lateral translation ofmovable trucks (not shown) supporting the substrate table. Additionalshield panels 184, 186 are arranged between the shield panel 182supporting the uniformity shield 152 and a second chamber adapter 132.The second chamber adapter 132 has a generally disc-like shapesurrounded by the load lock attachment flange 134, includes a firstaperture 136 supporting a second end of a drive screw suitable fortranslating a substrate table (not shown), and defines a rectangularaperture 140 generally aligned with the substrate table. The secondchamber adapter 132 further includes fasteners 138 for attachment ofdrive screw supports (not shown) along an inner surface of the secondchamber adapter 132. The first chamber adapter 122, which is bounded bythe substrate translation flange 124 and includes fasteners 128, isarranged at a first end of the lower and upper substrate tabletranslation rails 142, 178 opposing the second end where the secondchamber adapter 132 is located.

FIG. 13 is an upper perspective view of a portion of the reactor ofFIGS. 9 and 10, showing the collimator assembly 170 intermediatelyarranged between the target 166 of the linear sputtering apparatus 154and the deposition aperture 150 bounded in part by the uniformity shield152, and showing the substrate table 148 supported by movable trucks200A, 200B. Each movable truck 200A, 200B includes a body structure202A, 202B and lower wheels 204A, 204B that are received by a recess 144defined in the lower substrate table translation rail 142. Each movabletruck 200A, 200B further includes upper wheels (not shown) that arereceived by a similar recess defined in the upper substrate tabletranslation rail (not shown). The cathode body structure 156 includes ahollow interior containing liquid cooling channels 158, with the target166 arranged along a front of the cathode body structure 156 between thechannel guides 222 that enable collimator side brackets 162 supportingthe collimator assembly 170 to translate in a vertical direction. Incertain embodiments, a minimum distance between the target 166 and thedeposition aperture 150 is about 2 inches.

FIG. 14A is a side elevation view of a portion of the reactor of FIGS. 9and 10, showing a portion of a translation section arranged within thesecond tubular portion 120 (shown in FIG. 10), with the movablesubstrate table 148 supporting two substrates 214A, 214B (in dashedlines) in a first position. The deposition aperture 150 is bounded inpart by the shield panel 180 and the uniformity shield 152. A rotarydriver (such as a motor) 220 is arranged to rotate a drive screw (notshown) coupled to a follower (not shown) to translate the substratetable 148 in a horizontal direction. FIG. 14B is a side elevation viewof the reactor portion shown in FIG. 14A, with the substrate table 148in a different position following translation motivated by the rotarydriver 220. FIG. 14B shows a tubular guard 188 that contains a drivescrew (not shown) coupled to the rotary driver 220, with the tubularguard 188 defining a lateral slot 218 permitting movement of a follower(not shown) coupled to the drive screw.

FIG. 15A is a side elevation view of the substrate table 148 shown inFIGS. 13-14B, with the substrate table 148 including a support surface212 supporting two round substrates 214A, 214B, and including fasteners216 for mounting the substrates 214A, 214B to the support surface 212.FIG. 15B is a side elevation view of the substrate table 148 of FIGS.14A-15A, with the support surface 212 supporting four round substrates214A-214D and including corresponding fasteners 216. Although two orfour round substrates are shown in FIGS. 15A and 15B, it is to beappreciated that any suitable number of substrates of any desired shapesmay be supported by a single substrate table. In certain embodiments,each substrate includes a diameter of at least about 50 mm, at leastabout 100 mm, or at least about 150 mm.

FIG. 16 is a rear perspective view of the translation section 115 foruse within the reactor of FIGS. 9 and 10, including lower and uppersubstrate table translation rails 142, 178 as well as a tubular guard188 extending between drive screw supports 194, 196. A shield panel 180extends vertically between the lower and upper substrate tabletranslation rails 142, 178 and laterally between the deposition aperture150 and an end of the translation section 115. The tubular guard 188contains a drive screw terminating at a first end 127 extending throughthe drive screw support 194 for mating with a rotary driver (not shown),with a follower 190 coupled to the drive screw also being configured totranslate a movable truck 200B adapted to support a substrate table (notshown). The movable truck 200B includes lower wheels 204B received by arecess 144 defined in the lower substrate table translation rail 142 andupper wheels 206B received by a recess 198 defined in the uppersubstrate table translation rail 178. As illustrated, the movable truck200B is positioned proximate to the deposition aperture 150, andseparated from a fixed contact plate 211. The movable truck 200Bincludes a tab portion 208 extending rearward from the body structure202B and terminating at a leaf spring contact 210 (which may compriseberyllium copper), with the leaf spring contact 210 being configured tocontact the fixed contact plate 211 when the movable truck 200B istranslated toward the drive screw support 194 (as shown in FIG. 17). Thefixed contact plate 211 is in electrical contact with a substrate tableground strap 215 coupled to a terminal 213 arranged in communicationwith an electrical bias supply element (not shown) configured to apply abiasing voltage to the substrate table (not shown) when coupled to themovable truck 200B.

FIG. 17 is a magnified rear perspective view of the translation section115 of FIG. 16, following translation of the movable truck 200B towardone end of the translation section 115 to permit the leaf spring contact210 (shown in FIG. 16) to contact the fixed contact plate 211 and permita biasing voltage to be applied through the movable truck 200B to asubstrate table (not shown) coupleable to the movable truck 200B.Electrical biasing of the substrate table to a nonzero voltage desirablyenhances control of material deposition during sputtering. Translationof the movable truck 200B is motivated by the drive screw (containedwithin tubular guard 188) terminating at the first end 127, andfacilitated by rolling of the lower and upper wheels 204B, 206B inrecesses 144, 198 defined in the respective lower and upper substratetable translation rails 142, 178. The lower substrate table translationrail 142 defines a secondary slot 192 for receiving a shield panel (notshown) to enable repositioning of a uniformity shield (not shown)proximate to one edge of the deposition aperture 150.

FIG. 18 is a perspective assembly view of a portion of the translationsection 115 of FIGS. 16 and 17, showing lower and upper substrate tabletranslation rails 142, 178 and drive screw supports 194, 196 arrangedbetween first and second chamber adapters 122, 132. The tubular guard188 also extends between the drive screw supports 194, 196 and defines alateral slot 218 permitting translation of a follower 190 that iscoupled to a drive screw (not shown) within the tubular guard 188 and iscoupleable to a movable truck (not shown). The drive screw terminates ata first end 127 that extends through a first aperture 126 defined in thefirst chamber adapter 122 for coupling to a rotary driver (not shown).Fasteners 128 are provided to attach the drive screw supports 194, 196to inner surfaces of the first and second chamber adapters 122, 132.FIG. 18 shows the translation section 115 prior to attachment of twofixed sputter shield panels 180, 186 to the lower and upper substratetable translation rails 142, 178. Not shown are movable sputter shieldsthat may be received by a secondary slot 192 defined in the lowersubstrate table translation rail 142. Inserts 191 are further coupled tothe lower and upper substrate table translation rails 142, 178 proximateto the deposition aperture 150.

FIG. 19 is a perspective view of a portion of the reactor of FIGS. 9 and10, including the collimator assembly 170 and linear sputteringapparatus 154 (which is obscured by the collimator assembly 170) thatare insertable into the first tubular portion 102 shown in FIG. 9. FIG.19 further illustrates the recirculating ball screw drive mechanism 114and the collimator drive rotational seal 112 arranged to mate with adrive motor (not shown) that extend upward from the high voltage shield116 arranged above the collimator drive adapter flange 118. Therecirculating ball screw drive mechanism 114 is arranged to rotate adrive screw 230 that extends through the collimator drive adapter flange118 to engage a follower (not shown) coupled to the collimator assembly170 to promote vertical translation of the collimator assembly 170.Hollow guides 248 also extend through the collimator drive adapterflange 118 to convey liquid to and from liquid cooling channels in thecathode assembly (not shown). An electrically conductive mounting bar250 proximate to a lower surface of the collimator drive adapter flange118 is arranged between upper ends of channel guides 222 that definechannels 224, that extend in a vertical direction, and that are arrangedto receive collimator support bearing assemblies (not shown) which arecoupled to collimator side brackets 162. In combination with collimatorend brackets 226, the collimator side brackets 162 maintain thecollimator assembly 170 in a desired orientation. The collimatorassembly 170 includes multiple horizontal guide members 172 and multiplevertical guide members 174 that in combination form a grid definingmultiple apertures for guiding passage of metal atoms ejected from anejection surface of the target (not shown). Spacing between horizontalguide members 172 is maintained by tubular supports 176 that extend in avertical direction inboard of the collimator side brackets 162. Acollimator ground strap 168, which may be formed by a flexible springsteel band (e.g., made from steel tape measure material) connects thehorizontal and vertical guide members 172, 174 of the collimatorassembly 170 to ground, with the horizontal and vertical guide members172, 174 being electrically isolated from the collimator side brackets162 and collimator end brackets 226. Grounding of the horizontal andvertical guide members 172, 174 prevents any sputtering current fromflowing through bearings supporting the collimator assembly 170 withinchannels 224 defined in the channel guides 222, and from flowing throughthe drive screw 230 arranged to move the collimator assembly 170.

In certain embodiments, the collimator assembly 170 of FIG. 19 has amaximum travel distance of about 5.5 inches, and is configured to travelat a rate of about 0.2 inches per second in steps of 0.125 inch. Incertain embodiments, the collimator assembly 170 is moved to a travellength of about 3.5 inches, then the travel length is increased in stepsof about 0.125 inch until a travel length of 5.5 inches is attained,then the travel length is decreased in steps of 0.125 inch until atravel length of 3.5 inches is attained, and the process is repeated.Preferably, the entire ejection surface of the target is covered byhorizontal and vertical guide members 172, 174 of the collimatorassembly 170 at all positions of the collimator assembly 170 duringtravel.

FIG. 20 is a perspective assembly view of at least a portion of thecollimator assembly 170 of FIG. 19, including horizontal guide members172 and vertical guide members 174 arranged to cooperate with oneanother to form a grid. In certain embodiments, the horizontal guidemembers 172 and the vertical guide members 174 define slots to permitthe respective horizontal and vertical guide members 172, 174 to loadlock with one another. Spacing between horizontal guide members 172 ismaintained by tubular supports 176. In certain embodiments, thehorizontal guide members 172 and the vertical guide members 174 maycomprise grade 2 titanium sheet metal with a thickness of about 0.063inches, and the tubular supports 176 may also comprise grade 2 titanium.Rods 228 with threaded ends may be inserted through the tubular supports176 to maintain positioning of the horizontal and vertical guide members172, 174 and the tubular supports 176. In certain embodiments, spacingbetween horizontal guide members 172 may be about 0.75 inch, spacingbetween vertical guide members 174 may be about 0.688 inch to about0.731 inch, each horizontal guide member 172 may have a front-to-reardepth of about 0.5 inch, and each vertical guide member 174 may have afront-to-rear depth of about 0.574 inch.

FIG. 21 is a simplified schematic showing electrical connections toportions of a collimator assembly 170 and to a target 166 of a reactoraccording to FIGS. 9 and 10 according to one embodiment, includingindependent electrical control of different collimator guide members172, 174A-174F. As shown, the collimator assembly 170 is arranged in aconfiguration that is generally parallel to the target 166 associatedwith the linear sputtering apparatus 154. The collimator assembly 170includes horizontal guide members 172 optionally coupled to a firstpower source 231, with the horizontal guide members 172 being physicallyseparated from vertical guides 174A-174F (to prevent electricalinteraction therewith), and the vertical guides 174A-174F beingseparately coupled to independent power sources 229A-229F. Use ofindependent power sources coupled to different collimator guides 172,174A-174F enables enhanced control of sputter deposition when metalatoms ejected by the target 166 through the collimator assembly 170. Thelinear sputtering apparatus 154 arranged proximate to the target 166 iscoupled to a cathode power source 232. The horizontal guide members 172are separated from one another by tubular supports 176. The linearsputtering apparatus 154 and target 166 as well as the collimatorassembly 170 are arranged between collimator side brackets 162 andgenerally above a collimator end bracket 226. The collimator assembly170 is supported by the collimator side brackets 162 and is arranged totranslate vertically relative to the linear sputtering apparatus 154.Liquid ports 164 arranged along a top surface of the linear sputteringapparatus 154 are configured to circulate liquid through the linearsputtering apparatus 154 to transfer heat away therefrom duringsputtering operation.

FIG. 22 is a top plan view of a portion of the reactor of FIGS. 9 and 10visible through the upper flange 106 and first tubular portion 102,showing a collimator assembly 170 arranged between a linear sputteringapparatus 154 and a deposition aperture 150 that is bounded laterally bya uniformity shield 152 and a shield panel 180. The deposition aperture150 is also arranged below the upper substrate table translation rail178. As shown, the collimator assembly 170 is arranged in aconfiguration that is generally parallel to the target 166 associatedwith the linear sputtering apparatus 154. The horizontal guide members172 of the collimator assembly 170 are physically separated fromvertical guides 174, with the horizontal and vertical guide members 172,174 being arranged generally above a collimator end bracket 226 andgenerally arranged between collimator side brackets 162. An ejectionsurface of the target 166 is arranged to eject metal atoms throughapertures defined by horizontal and vertical guide members 172, 174 ofthe collimator assembly 170 toward the deposition aperture 150 and asubstrate (not shown). Liquid ports 164 are provided along a top surfaceof the linear sputtering apparatus 154 for cooling thereof.

FIG. 23 is a top plan view of the reactor portion of FIG. 22, with thecollimator assembly 170 and the linear sputtering apparatus 154 in asecond configuration, wherein the collimator assembly 170 is arranged ata first angle non-parallel to the deposition aperture 150 (and asubstrate (not shown) behind the deposition aperture 150), and thelinear sputtering apparatus 154 (and associated target 166) is arrangedat a second angle non-parallel to the deposition aperture 150, whereinthe second angle is greater than the first angle. The horizontal guidemembers 172 of the collimator assembly 170 are physically separated fromvertical guide members 174, with the guide members 172, 174 beinggenerally above a collimator end bracket 226 and generally arrangedbetween collimator side brackets 162. An ejection surface of the target166 is arranged to eject metal atoms through apertures defined by guidemembers 172, 174 of the collimator assembly 170 toward the depositionaperture 150 and a substrate (not shown). As shown, a leftmostcollimator side bracket 162 interferes with a shield panel 180,demonstrating that modification of size or shape of the shield panel 180or the collimator side bracket 162 (and collimator end bracket 226) maybe necessary to achieve the positioning shown in FIG. 23. Other elementsshown in FIG. 23 are generally the same as shown in FIG. 22.

FIG. 24 is a cross-sectional view of a portion of the reactor of FIGS. 9and 10, showing the target 166 arranged between the linear sputteringapparatus 154 and the collimator assembly 170, with the collimatorassembly 170 arranged non-parallel to an ejection surface of the target166. Superimposed in dashed lines over the collimator assembly 170 andthe collimator ground strap 168 are the drive screw 230 and therecirculating ball screw drive mechanism 114, which are configured topromote vertical translation of the collimator assembly 170. Thecollimator assembly 170 includes multiple horizontal guide members 172and multiple vertical guide members 174 that in combination form a griddefining multiple apertures for guiding passage of metal atoms ejectedfrom an ejection surface of the target 166. Spacing between horizontalguide members 172 is maintained by tubular supports 176 that extend in avertical direction, generally inboard of the collimator side brackets162 and above a collimator end bracket 226. Vertical movement betweenthe collimator end bracket 226 and channels 224 defined by the channelguides 222 is provided by bearings 160. The linear sputtering apparatus154 includes a cathode body structure 156 supporting center pole magnets236 and perimeter magnets 238, with the cathode body structure 156further including a hollow interior containing liquid cooling channels158 bounded by thermally conductive (e.g., copper) inserts 240. Incertain embodiments, the magnets 236, 238 may comprise NdFeB blockmagnets with nickel (e.g., Ni—Cu—Ni) plating. In certain embodiments,the perimeter magnets 238 in combination form a rounded rectangular(e.g., racetrack) shape, and the center pole magnets 236 form a linearshape. A thermally conductive (e.g., copper) backing plate 234 isprovided between the thermally conductive inserts 240 and the target166. Conductive elements 242 are further arranged around lateralboundaries of the cathode body structure 156 that is coincident with theperimeter of the target 166 and the thermally conductive backing plate234.

FIG. 25 is a perspective cross-sectional view of a portion of the linearsputtering apparatus 154 shown in FIG. 24 and useable in the reactor ofFIGS. 9 and 10. A cathode body structure 156 supports center polemagnets 236 (preferably arranged in a line) and perimeter magnets 238(preferably arranged in a rounded horizontal configuration). The cathodebody structure 156 further defines a cavity 244 containing liquidcooling channels 158 bounded by thermally conductive inserts 240 andbounded by the thermally conductive backing plate 234, which abuts thetarget 166. The target 166 preferably consists of a pure metal (e.g.,99.999% pure aluminum or zinc). Lateral edges of the cathode bodystructure 156 and the perimeter magnets 238 are bounded by conductiveelements 242.

FIG. 26 is a perspective view of the cathode body structure 156 andmagnets 236, 238 of the linear sputtering apparatus 154 shown in FIG. 25and useable in the reactor of FIGS. 9 and 10. A peripheral portion ofthe cathode body structure 156 forms a rounded rectangular shapesupporting the perimeter magnets 238, and an inner portion of thecathode body structure 156 forms an elevated linear wall 156A supportingthe center pole magnets 236. The cathode body structure 156 forms acavity 244. Along one end, the cathode body structure 156 definesapertures 246 to enable liquid to flow to and from liquid coolingchannels 158 (shown in FIG. 25).

FIG. 27 is a perspective view of the linear sputtering apparatus 154mounted between end caps 157 and the channel guides 222 for use with thereactor of FIGS. 9 and 10. Each end cap 157 may be formed of insulatingconductive material, and preferably includes a curved surface (notshown) to abut a curved end of the cathode body structure 156 shown inFIG. 26. An electrically conductive mounting bar 250 is arranged betweenupper ends of channel guides 222 (which include channels 224), anddefines liquid ports 164 coupled to hollow guides 248 that guide liquidconveying tubes connected to the thermally conductive backing plate 234.As shown, an ejection surface of the target 166 is exposed to permitejection of metal atoms during sputtering operation.

FIG. 28 is a perspective view of an alternative collimator assembly 155arranged within the first tubular portion 102 of a deposition reactor,with vertical guide members 174A-174F separated by tubular supports 176and extending in a single direction. Electrical conductors 254A-254F arearranged in communication with individual vertical guide members174A-174F for separate application of voltage to different verticalguide members 174A-174F for electrical biasing thereof, to enhancecontrol of material deposition when a sputtering cathode assembly andtarget surface (not shown) are arranged proximate to the collimatorassembly 155. As shown, the vertical guide members 174A-174F arearranged proximate to a deposition aperture bounded by shield panels180, 182 and a uniformity shield 152, with the vertical guide members174A-174F being angled (or inclined) relative to two substrates 214A,214B to guide the passage of metal atoms (e.g., aluminum or zinc) thatreact with a gas species (e.g., nitrogen or oxygen) within the reactorto deposit crystalline seed material and/or hexagonal crystal structurepiezoelectric material over the substrates 214A, 214B. Preferably,deposited piezoelectric material includes a c-axis having an orientationdistribution predominantly in a range of from 25 degrees to 50 degrees(or in a subrange of from 30 degrees to 40 degrees) relative to normalof a face of the substrates 214A, 214B. In certain embodiments, eachsubstrate 214A, 214B is circular in shape and includes a diameter ofabout 100 mm.

In certain embodiments, a collimator assembly is configured to move(e.g., translate) during operation of a linear sputtering apparatus,such as to prevent formation of a “shadow” pattern that would otherwisebe formed on a surface (e.g., substrate or wafer) receiving depositedpiezoelectric material following transit of metal atoms through thecollimator assembly. Such a collimator assembly is preferablyelectrically biased to a non-zero voltage during sputtering operation.FIGS. 29A and 29B provide plots of bias voltage versus time foroperation of an electrically biased collimator that forms atwo-dimensional grid, such as shown in FIG. 19. FIG. 29A shows a biasvoltage that varies from about 2 V to about 14 V, FIG. 29B shows thatthe bias voltage has a primary oscillation frequency of about 3 Hz, andFIG. 29A shows that the bias voltage further exhibits secondaryoscillations that are due to translation of the collimator assembly.

In certain embodiments, a deposition system includes multiple linearsputtering apparatuses, a substrate table that is translatable betweendifferent positions (e.g., at different stations and/or to differentchambers) proximate to different linear sputtering apparatuses, and oneor more collimators arranged between the substrate table and one or moreof the respective linear sputtering apparatuses, with a support surfaceof the substrate table being non-parallel to at least one target surfaceof the different linear sputtering apparatuses. A representativedeposition system 300 including multiple linear sputtering apparatusesis shown in FIGS. 30A and 30B. FIG. 30A illustrates components andpiping connections of the deposition system 300, and FIG. 30B includesrepresentation of thermal and control components of the depositionsystem 300.

Referring to FIG. 30A, the deposition system 300 includes a load lockchamber 302 including an exterior door 304 and a transition door 306,with the load lock chamber 302 being intermediately arranged between adeposition enclosure 334 and an exterior environment to enable transferof a substrate table 322 and substrates 326 without exposing thedeposition enclosure 334 to atmospheric conditions. Contents of the loadlock chamber 302 and/or the deposition enclosure 334 may be ventedthrough valves 400, 406 to a vent 422. A vacuum gauge 330 and pressureswitches 332 are in sensory communication with the load lock chamber302. After the substrate table 322 with substrates 326 supported by asupport surface 324 is loaded through the exterior door 304 into theload lock chamber 302, a roughing pump 418 and/or a turbomolecularvacuum pump 410 in combination with valves 402, 408, 412 (and a pressureswitch 416) may be used to extract gaseous contents of the load lockchamber 302 through an exhaust 420 in order to establish asubatmospheric pressure condition in the load lock chamber 302.Thereafter, the substrate table 322 and substrates 326 may be loadedthrough the transition door 306 into the deposition enclosure 334, whichincludes a first station 334A and a second station 334B, optionallydivided by a wall or partition 336 whereby the first station 334A may beprovided in a first chamber and the second station 334B may be providedin a second chamber. Although FIG. 30A illustrates both stations 334A,334B as being provided in a single deposition enclosure 334, it is to berecognized that in certain embodiments, separate first and secondchambers (not shown) containing the first and second stations 334A,334B, respectively, may be provided. In such an instance, such chambersare preferably selectively isolated relative to one another, with afirst vacuum pumping element being associated with the first chamber anda second vacuum pumping element being associated with the secondchamber. Continuing to refer to FIG. 30A, a background gas shower nozzle354 positioned within the deposition enclosure 334 is configured toreceive background gas (e.g., an inert gas such as Argon) from abackground gas source 364 and a valve 366. In certain embodiments, thesubstrate table 322 bearing substrates 326 is initially positioned atthe first station 334A for deposition of a crystalline seed layer overthe substrates 326, and thereafter the substrate table 322 andsubstrates 326 are moved (e.g., translated) to the second station 334Bfor deposition of a hexagonal crystal structure piezoelectric materialbulk layer over the crystalline seed layer. A differential pump 370 isalso provided between the deposition enclosure 334 and the roughing pump418 proximate to the exhaust 420.

The first station 334A includes a first sputtering cathode assembly 344Aarranged to discharge metal atoms from an ejection surface of a firsttarget 346A to transit through a first collimator assembly 348A towardthe substrates 326. A magnetron gas source 360A and an associated valve362A are arranged to supply gas (preferably including a gas that isreactive with the metal atoms, such as nitrogen or oxygen) to gasnozzles 340A arranged downstream of the first collimator assembly 348A.An additional (shower) gas source 356A and an associated valve 358A arearranged to supply additional gas to gas nozzles 342A arranged proximateto the first target 346A. The first sputtering cathode assembly 344A andthe first collimator assembly 348A are preferably supported by (e.g.,suspended from) a first large flange 350A and a first small flange 352Athat is not coaxially aligned with the first large flange 350A, wherebythe first large flange 350A may be repositioned to adjust distancebetween the first target 346A and the substrates 326, and the firstsmall flange 352A may be repositioned to adjust a tilt angle of thefirst sputtering cathode assembly 344A (and the first collimatorassembly 348A) relative to the substrates 326. As shown in FIG. 30A, thefirst sputtering cathode assembly 344A and the first collimator assembly348A may be positioned at a relatively shallow angle relative to thesubstrates 326, in order to promote growth of a crystalline seed layerincluding a c-axis having an orientation distribution predominantly in arange of from 0 degrees to 35 degrees relative to normal of a face ofthe substrates 326.

The second station 334B includes a second sputtering cathode assembly344B arranged to discharge metal atoms from an ejection surface of asecond target 346B to transit through a second collimator assembly 348Btoward the substrates 326. A movable truck 338 including electricalbiasing hardware is arranged proximate to the substrate table 322 totranslate the substrate table 322 and bias the substrate table 322 to anelectrical potential other than ground to enhance control of materialdeposition during use of the second sputtering cathode assembly 344B. Amagnetron gas source 360B and an associated valve 362B are arranged tosupply gas (preferably including a gas that is reactive with the metalatoms) to gas nozzles 340B arranged downstream of the second collimatorassembly 348B. An additional (shower) gas source 356B and an associatedvalve 358B are arranged to supply additional gas to gas nozzles 342Barranged proximate to the second target 346B. The second sputteringcathode assembly 344B and the second collimator assembly 348B arepreferably supported by (e.g., suspended from) a second large flange350B and a second small flange 352B that is not coaxially aligned withthe second large flange 350B, whereby the second large flange 350B maybe repositioned to adjust distance between the second target 346B andthe substrates 326, and the second small flange 352B may be repositionedto adjust a tilt angle of the second sputtering cathode assembly 344B(and the second collimator assembly 348B) relative to the substrates326. As shown in FIG. 30A, the second sputtering cathode assembly 344Band the second collimator assembly 348B may be positioned at a steeperangle relative to the substrates 326, in order to promote growth of ahexagonal crystal structure piezoelectric material bulk layer includinga c-axis having an orientation distribution predominantly in a range offrom 25 degrees to 50 degrees (or in a subrange of from 30 degrees to 40degrees) relative to normal of a face of the substrates 326. Furtherprovided in sensory communication with the deposition enclosure 334 arepressure switches 372 and vacuum gauges 368, 374. The latter vacuumgauge 374 is arranged to provide feedback to a valve 388 arrangedbetween the deposition enclosure 334 and a cryogenic pumping system 376,which includes a cryopump 380, an overpressure valve 384, a cryopumpingexhaust valve 386, and a purge valve 382 coupled to a purge gas source378. The cryopump 380 is further coupled with a cryocompressor 392. Thecryopumping exhaust valve 386 and an enclosure exhaust valve 390 areboth coupled to exhaust piping monitored by a vacuum gauge 396 andcoupled to a roughing pump 394 arranged to remove gas to an exhaust 398.

Referring to FIG. 30B, the load lock chamber 302 of the depositionsystem 300 includes a substrate heater 312 arranged to receive powerfrom a transformator 316 to heat the substrates 326 supported by thesupport surface 324 of the substrate table 322, and includes substratetable heaters 314 arranged to receive power from a transformator 318 toheat the substrate table 322. A load lock chamber heating controller 320is arranged to receive temperature feedback signals from a substratepyrometer 308 and a substrate table pyrometer 310 to provide controlsignals to the transformators 316, 318. The heaters 312, 314 may be usedto eliminate any vapor (e.g., water vapor and/or cleaning solvent) fromthe substrates 326 and the substrate table 322 that may be present afterloading the substrate table 322 and substrates 326 through the exteriordoor 304. After vapor removal is complete and appropriate subatmosphericconditions are established in the load lock chamber 302, the substratetable 322 and substrates 326 may be moved through the transition door306 into the deposition enclosure 334, preferably to a first station334A proximate to the first sputtering cathode assembly 344A. As notedpreviously, the deposition enclosure 334 may be subdivided into a firststation 334A and a second station 334B, optionally divided by a wall orpartition 336; alternatively, a first station may be provided in a firstchamber, and a second station may be provided in a second chamber,wherein the respective stations are preferably selectively isolatablerelative to one another. Continuing to refer to FIG. 30B, the depositionenclosure 334 includes a chamber heater 448 coupled to a heating element446. Additionally, localized heating of the substrate table 322 may beaccomplished with heaters (e.g., infrared heaters) 424A-424C eachcoupled to a corresponding heating transformator 426A-426C that iscontrolled by a deposition enclosure heating controller 430 thatreceives temperature feedback signals from pyrometers 436A-436C arrangedproximate to the heaters 424A-424C. A first DC generator 442A coupled toa reactive sputtering controller 440 is arranged to supply power to thefirst sputtering cathode assembly 344A, and a first crystal oscillatormonitor 428A coupled to a first oscillator 438A is provided to monitorthe first target 346A to provide information regarding materialdeposition rate during operation of the first sputtering cathodeassembly 344A. A second DC generator 442B coupled to the reactivesputtering controller 440 is arranged to supply power to the secondsputtering cathode assembly 344B, and a second crystal oscillatormonitor 428B coupled to a second oscillator 438B is provided to monitorthe second target 346B to provide information regarding materialdeposition rate during operation of the second sputtering cathodeassembly 344B. Thickness of one or more material films deposited overthe substrates 326 is monitored with a film thickness monitor 444. Aradio frequency generator 432 and a transformator 434 are coupled toelectrical biasing hardware associated with a movable truck 338 arrangedproximate to the substrate table 322 to bias the substrate table 322 toan electrical potential other than ground to enhance control of materialdeposition during use of the second sputtering cathode assembly 344B.The first sputtering cathode assembly 344A and the first collimatorassembly 348A are preferably supported by (e.g., suspended from) a firstlarge flange 350A and a first small flange 352A that is not coaxiallyaligned with the first large flange 350A, and the second sputteringcathode assembly 344B and the second collimator assembly 348B arepreferably supported by (e.g., suspended from) a second large flange350B and a second small flange 352B that is not coaxially aligned withthe second large flange 350B.

Preferably, a crystalline seed layer as described herein is grown overthe substrates 326 at the first station 334A using the first sputteringcathode assembly 344A (optionally in conjunction with the firstcollimator assembly 348A), then the substrate table 322 supporting thesubstrates 326 is moved (e.g., translated) to the second station 334B,and a hexagonal crystal structure piezoelectric material bulk layer asdescribed herein is grown over the crystalline seed layer at the secondstation 334B. In this manner, a second growth step (for growing apiezoelectric material bulk layer such as aluminum nitride or zincoxide) may be performed in a sequential manner in a subatmosphericenvironment following the first growth step (for growing the crystallineseed layer) without any need for removing the at least one resonatordevice complex into an atmospheric pressure environment before thesecond growth step (e.g., which would otherwise require significant timeand energy to establish subatmospheric conditions at the second station334B, and may otherwise require performance of additional steps to avoidintroduction of particulates and other contaminants that could lead todefects in finished devices).

Various embodiments disclosed herein relate to use of at least onelinear sputtering apparatus and at least one multi-aperture collimatorfor depositing a crystalline seed layer over a substrate, and fordepositing a tilted c-axis hexagonal crystal structure piezoelectricmaterial bulk layer over the crystalline seed layer (with the c-axishexagonal crystal structure piezoelectric material bulk layer beingcompositionally matched to the crystalline seed layer in preferredembodiments). It has been determined that providing a crystalline seedlayer below the piezoelectric material bulk layer beneficially enables agreater angle of c-axis distribution range than can be achieved in theabsence of a crystalline seed layer (as apparent by comparison of FIGS.31 and 32), and that increasing pressure during deposition of thecrystalline seed layer increases uniformity of the c-axis angulardistribution range of the piezoelectric material bulk layer (as apparentby comparison of FIGS. 32 and 33). Such points are further detailedbelow.

FIG. 31 is a plot of intensity versus c-axis angle for X-ray diffractionanalysis of a tilted c-axis AlN bulk layer formed over a substratewithout an intervening seed layer. As shown, peak intensity is shown ata c-axis angle of about 7 degrees, with the angular distributiondeclining in a nearly asymptotic manner for c-axis angles greater thanabout 16 degrees, exhibiting negligible intensity for c-axis anglesabove about 20 degrees. FIG. 32 is a plot of intensity versus c-axisangle for X-ray diffraction analysis of a tilted c-axis AlN bulk layerformed over an AlN seed layer supported by a substrate (of the same typeused in FIG. 31 and grown in the same apparatus under similar AlN layergrowth conditions), with the seed layer formed at a deposition pressureof 5 mT.

In contrast to FIG. 31, FIG. 32 shows attainment of peak intensity at ac-axis angle of about 30 degrees, with a substantially smaller secondarypeak visible around 7 degrees, wherein the intensity value of thesecondary peak is less than about one eighth the intensity value of theprimary peak visible at about 30 degrees. FIGS. 31 and 32 in combinationtherefore evidence that presence of crystalline AlN seed materialenables growth of an AlN bulk layer having a greater c-axis tilt anglethan can be attained by depositing an AlN bulk layer over a substratewithout an intervening seed layer. As noted above, increasing depositionpressure for growth of the crystalline seed layer has been found toincrease uniformity of the c-axis angular distribution range of thepiezoelectric material bulk layer. FIG. 33 is a plot of intensity versusc-axis angle for X-ray diffraction analysis of a tilted c-axis AlN bulklayer formed over an AlN seed layer supported by a substrate, with theseed layer formed at a comparatively higher pressure of 15 mT. Growth ofcrystalline AlN seed material at 15 mT takes significantly longer thangrowth of the same thickness of crystalline AlN seed material at 5 mT,but leads to attainment of higher quality in a subsequently depositedAlN bulk layer. In contrast to FIG. 32, FIG. 33 shows near-zerointensity values (i.e., less than about 3 percent) for c-axis angles ina range of from about 0 to 15 degrees. The absence of a significantsecondary peak in a c-axis tilt angle range of from about 0 to 15degrees is expected to increase the ratio of shear coupling coefficientrelative to longitudinal coupling coefficient for the piezoelectric bulkmaterial, thereby providing increased shear coupling for enhancedresponse of resonator devices useable in liquids or other viscous media.Thus, in certain embodiments, less than about 3 percent of a c-axisorientation distribution of a hexagonal crystal structure piezoelectricmaterial bulk layer is in a range of from 0 degrees to 15 degreesrelative to normal of a face of the substrate of a bulk acoustic waveresonator device.

FIG. 34 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) versus c-axis angleof inclination for AlN, with such plot being derivable from the plot ofFIG. 3. As shown in FIG. 34, the shear/long ratio increases more thanthreefold by increasing the c-axis angle of inclination of AlN from 20degrees to 30 degrees. For biochemical sensing applicationsincorporating bulk acoustic wave resonator devices, shear/long ratiosare preferably greater than 1, more preferably at least 1.25, morepreferably at least 2, and still more preferably at least 3.

FIG. 35 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) for a first set ofeight AlN film samples (including AlN bulk material) grown according tothree growth conditions (i.e., no seed layer, presence of an AlN seedlayer grown at 5 mT, and presence of an AlN seed layer grown at 15 mT).The horizontal dashed line represents a desired minimum shear/long ratiovalue of 1.25. As shown, the shear/long ratio was less than 0.5 for allfour samples with no seed layer, and was also less than 0.5 for thesingle sample including a seed layer grown at 5 mT. In contrast, theshear/long ratio values for all samples that included a seed layer grownat 15 mT were greater than 1.5. This data set shows that shear/longratio may be enhanced by the presence of an AlN seed layer grown at 15mT.

FIG. 36 is a plot of squared shear coupling coefficient over squaredlongitudinal coupling coefficient (shear/long ratio) for a second set oftwenty-four AlN film samples grown according to three growth conditions(i.e., no seed layer, presence of an AlN seed layer grown at 5 mT, andpresence of an AlN seed layer grown at 15 mT). The horizontal dashedline represents a desired minimum shear/long ratio value of 1.25. Asshown, the shear/long ratio was less than 0.5 for all five samples withno seed layer, while shear/long ratio values varied from a minimum ofabout 0.5 to a maximum of nearly 2.5 (with an average value closer toabout 1.2) for the fourteen samples including a seed layer grown at 5mT. Significant variability in shear/long ratio values was exhibited bythe samples including a seed layer grown at 5 mT. In contrast, theshear/long ratio was greater than 1.25 for all five samples with a seedlayer grown at 15 mT, demonstrating a higher average shear/long ratioand less variability in shear/long ratio as compared to the samplesgrown at 5 mT.

Hexagonal crystal structure piezoelectric materials, such as AlN grownutilizing systems and methods disclosed herein, preferably exhibitcontrolled stress and densely packed columnar grains or recrystallizedgrain structure. FIG. 37A is a cross-sectional scanning electrodemicroscopy (SEM) photograph (50,000× magnification) of an AlN bulk layer450A deposited over an AlN seed layer (barely visible) grown at 5 mT andan aluminum thin film 452A over a substrate 454A. The AlN seed layer isvertically aligned, and a transition to the AlN bulk layer 450A is wheretilted AlN grains initiate growth. FIG. 37B is a SEM photograph (50,000×magnification) of a top surface of the AlN bulk layer 450A of FIG. 37A.For comparison, FIG. 38A is a cross-sectional SEM photograph (50,000×magnification) of an AlN bulk layer 450B deposited over an AlN seedlayer (barely visible) grown at 15 mT over an aluminum thin film 452Band over a substrate 454B, and FIG. 38B is a SEM photograph (50,000×magnification) of a top surface of the AlN bulk layer 450B of FIG. 38A.As shown in the foregoing four figures, the AlN bulk layer 450B providedover an AlN seed layer at 15 mT exhibits a denser and more regular grainstructure than the AlN bulk layer 450A grown over an AlN seed layergrown at 5 mT. This appears consistent with a comparison between FIGS.32 and 33, in which less variability in c-axis tilt angle was found foran AlN bulk layer provided over an AlN seed layer grown at 15 mT thanfor an AlN bulk layer provided over an AlN seed layer grown at 5 mT.

FIG. 39 is a cross-sectional view SEM photograph (50,000× magnification)of an AlN bulk layer having a c-axis tilted 35 degrees relative tonormal of an underlying substrate. The AlN bulk layer was depositedusing a collimator-to-substrate angle of 36 degrees utilizing adeposition reactor according to the design of FIGS. 9 and 10.

As noted previously, electrical biasing of the substrate table and/orthe collimator to a potential other than ground may be utilized duringdeposition of piezoelectric material such as AlN. FIG. 40A is across-sectional SEM photograph (50,000× magnification) of a portion ofan AlN bulk layer grown at 1.2 mT without the use of an AlN seed layerand without the use of collimator biasing. FIG. 40B is a cross-sectionalSEM photograph (75,000× magnification) of a portion of the same film ofFIG. 40A, with the AlN bulk layer exhibiting a c-axis tilt angle of 9.63degrees relative to normal of a substrate. For comparison, FIG. 41A is across-sectional SEM photograph (50,000× magnification) of a portion ofan AlN bulk layer grown at 0.6 to 0.8 mT with use of collimator biasingat 60V. FIG. 41 B is a cross-sectional SEM photograph (75,000×magnification) of a portion of the same film of FIG. 41A with an AlNbulk layer grown without the use of an AlN seed layer but with the useof collimator biasing. The AlN bulk layer of FIG. 41B exhibits a c-axistilt angle of 6.83 degrees relative to normal of a substrate. A visualcomparison between FIGS. 40B and 41B suggests that the use of collimatorbiasing may result in more densely packed columnar grains orrecrystallized grain structure. Separately, Applicant has found thatcollimator biasing tends to improve influence microstructure developmentof tilted c-axis piezoelectric bulk material in a bulk acoustic waveresonator device.

Embodiments as disclosed herein may provide one or more of the followingbeneficial technical effects: enablement of growing inclined c-axishexagonal crystalline material films (preferably of high tilt angles)over large area substrates without significant variation in c-axis tiltangle, facilitating efficient manufacture of c-axis hexagonalcrystalline material films of high tilt angles over large areasubstrates for production of bulk acoustic wave resonator structures;and enhanced control of deposition of inclined c-axis hexagonalcrystalline material films.

Upon reading the following description in light of the accompanyingdrawing figures, those skilled in the art will understand the conceptsof the disclosure and will recognize applications of these concepts notparticularly addressed herein. Those skilled in the art will recognizeimprovements and modifications to the preferred embodiments of thepresent disclosure. All such improvements and modifications areconsidered within the scope of the concepts disclosed herein and theclaims that follow. Any of the various features and elements asdisclosed herein may be combined with one or more other disclosedfeatures and elements unless indicated to the contrary herein.

What is claimed is:
 1. An acoustic resonator structure comprising: asubstrate; at least one first electrode structure supported by thesubstrate; a crystalline seed layer arranged over the substrate and theat least one first electrode structure; a hexagonal crystal structurepiezoelectric material bulk layer arranged over the crystalline seedlayer; and at least one second electrode structure arranged over atleast a portion of the hexagonal crystal structure piezoelectricmaterial bulk layer; wherein at least 50% of the hexagonal crystalstructure piezoelectric material bulk layer comprises a c-axis having anorientation distribution predominantly in a range of from 25 degrees to50 degrees relative to normal of a face of the substrate.
 2. Theacoustic resonator structure of claim 1, wherein the crystalline seedlayer is compositionally matched to the hexagonal crystal structurepiezoelectric material bulk layer.
 3. The acoustic resonator structureof claim 1, wherein a thickness of the crystalline seed layer is nogreater than about 20% of a combined thickness of the hexagonal crystalstructure piezoelectric material bulk layer and the crystalline seedlayer.
 4. The acoustic resonator structure of claim 1, wherein thecrystalline seed layer comprises a thickness in a range of from about500 Angstroms to about 2,000 Angstroms.
 5. The acoustic resonatorstructure of claim 1, wherein at least 50% of the crystalline seed layercomprises a c-axis having an orientation distribution predominantly in arange of from 0 degrees to 35 degrees relative to normal of a face ofthe substrate.
 6. The acoustic resonator structure of claim 1, whereinthe hexagonal crystal structure piezoelectric material bulk layercomprises a thickness in a range of from about 4,000 Angstroms to about26,000 Angstroms.
 7. The acoustic resonator structure of claim 1,wherein the substrate comprises a semiconductor material.
 8. Theacoustic resonator structure of claim 1, further comprising an acousticreflector structure arranged between the substrate and the at least onefirst electrode structure.
 9. The acoustic resonator structure of claim8, wherein the substrate is arranged between a backside surface and theacoustic reflector structure, and the backside surface comprises aroughened surface configured to reduce or eliminate backside acousticreflection.
 10. The acoustic resonator structure of claim 1, wherein thesubstrate defines a recess, a support layer is arranged over the recess,and the support layer is arranged between the substrate and at least aportion of the at least one first electrode structure.
 11. The acousticresonator structure of claim 1, wherein at least 90% of the hexagonalcrystal structure piezoelectric material bulk layer comprises a c-axishaving an orientation distribution predominantly in a range of from 25degrees to 50 degrees relative to normal of a face of the substrate. 12.The acoustic resonator structure of claim 1, wherein at least 50% of thehexagonal crystal structure piezoelectric material bulk layer comprisesa c-axis having an orientation distribution predominantly in a range offrom 30 degrees to 40 degrees relative to normal of a face of thesubstrate.
 13. The acoustic resonator structure of claim 1, wherein lessthan about 3 percent of the c-axis orientation distribution of thehexagonal crystal structure piezoelectric material bulk layer is in arange of from 0 degrees to 15 degrees relative to normal of a face ofthe substrate.
 14. The acoustic resonator structure of claim 1, whereinthe substrate comprises a diameter of at least about 50 mm, and thehexagonal crystal structure piezoelectric material bulk layer covers atleast about 50% of a face of the substrate.
 15. The acoustic resonatorstructure of claim 1, wherein the substrate comprises a diameter of atleast about 100 mm, and the hexagonal crystal structure piezoelectricmaterial bulk layer covers at least about 50% of a face of thesubstrate.
 16. The acoustic resonator structure of claim 1, wherein thehexagonal crystal structure piezoelectric material bulk layer comprisesaluminum nitride or zinc oxide.
 17. The acoustic resonator structure ofclaim 1, wherein: the at least one first electrode structure comprises aplurality of first electrode structures; the at least one secondelectrode structure comprises a plurality of second electrodestructures; a first portion of the acoustic resonator structurecomprises a first bulk acoustic wave resonator device including a firstactive region arranged between one first electrode structure of theplurality of first electrode structures and one second electrodestructure of the plurality of second electrode structures; and a secondportion of the acoustic resonator structure comprises a second bulkacoustic wave resonator device including a second active region arrangedbetween another first electrode structure of the plurality of firstelectrode structures and another second electrode structure of theplurality of second electrode structures.
 18. A bulk acoustic waveresonator chip derived from the acoustic resonator structure of claim17.
 19. A sensor or microfluidic device incorporating the bulk acousticwave resonator chip of claim 18.